Skip to main content

Full text of "HEATING VENTILATING AIR CONDITIONING GUIDE 1938 VOL. 16"

See other formats


1 03  748 


697    451        1938 


HEATING  VENTILATING 

AIR  CONDITIONING 

GUIDE   1938 


TEXT     .AND     ILLUSTRATIONS     -ARE      KXIJLLY      PRO- 
TECTED    SY     COPYRIGHT     .A.ND     NOTHING 
AF*I>EARS    M:AY    BE    REJ»RJNTED    EITHER 
OR     Z>T     P-ART     \VITHOtTT     SPEGJjVL     PER1V4TIS  SION . 


HEATING  VENTILATING 
AIR  CONDITIONING 

GUIDE 

1938 

AN  INSTRUMENT  OF  SERVICE  PREPARED  FOR  THE  PROFESSION — CONTAINING  A 

Technical  Data  Section 

OF  REFERENCE  MATERIAL  ON  THE  DESIGN  AND  SPECIFICATION  OF  HEATING, 
VENTILATING  AND  AIR  CONDITIONING  SYSTEMS — BASED  ON  THE  TRANS- 
ACTIONS— THE  INVESTIGATIONS  OF  THE  RESEARCH  LABORATORY  AND  CO- 
OPERATING INSTITUTIONS — AND  THE  PRACTICE  OF  THE  MEMBERS  AND 
FRIENDS  OF  THE  SOCIETY 

TOGETHER  WITH  A 

Manufacturers9  Catalog  Data  Section 

CONTAINING  ESSENTIAL  AND  RELIABLE  INFORMATION  CONCERNING 
MODERN  EQUIPMENT 

ALSO 

The  Roll  of  Membership  of  the  Society 

WITH 

Complete  Indexes 

TO  TECHNICAL  AND  CATALOG  DATA  SECTIONS 

Vol.  16 

$5.00  PER  COPY 
Copyright,  1938 

AND 

PUBLISHED  ANNUALLY  BY 

AMERICAN  SOCIETY  OF  HEATING  AND  VENTILATING  ENGINEERS 

51  MADISON  AVENUE          .'.          NEW  YORK,  N.  Y. 


"TO  THE  isth  EDITION 

J^HE  acceptance    of    the    HEATING,    VENTILATING,    AIR 

CoxDiTi6>'i>:Gt  GUIDE  as  an  authoritative  source  of  scientific  infor- 
mation on  all  engineering  phases  of  the  industry,  has  imposed  each  year 
since  1922  more  and  greater  responsibilities  on  the  Guide  Publication 
Committee.  Although  extensive  new  material  has  been  added  to  this 
edition,  the  ideals  of  the  founders  have  been  carefully  preserved  by  pre- 
senting only  authentic  and  current  investigative  results  which  have  been 
tried  and  accepted  in  practice. 

The  sequence  and  arrangement  of  the  various  chapters  have  been 
changed  to  provide  for  a  more  logical  grouping  according  to  related 
subject  matter,  and  a  visual  chapter  index  has  been  added.  Probably, 
the  greatest  changes  that  have  been  made  in  the  text  are  those  relating 
to  cooling  phases  of  the  industry.  The  chapters  on  Refrigerants  and  Air 
Drying  Agents,  Cooling  Load,  Central  Systems  for  Cooling  and  Dehu- 
midifying  and  Cooling  and  Dehumidification  Methods  have  been  entirely 
revised  to  bring  them  up-to-date  and  to  correlate  them  more  closely. 
One  entirely  new  chapter  on  Air  Conditioning  in  the  Treatment  of 
Disease  was  introduced  in  this  edition  which  outlines  many  of  the  appli- 
cation requirements  found  in  the  medical  field.  Some  minor  changes  were 
made  in  the  chapters  on  Heat  Transmission  Coefficients,  Air  Leakage, 
Heat  and  Fuel  Utilization,  Heating  Boilers  and  Steam  Heating  Systems. 

The  chapters  have  been  rewritten  which  deal  with  Air  Pollution, 
Automatic  Fuel  Burning  Equipment,  Hot  Water  Heating  Systems  and 
Piping,  Spray  Equipment  for  Humidification  and  Dehumidification,  Air 
Cleaning  Devices,  Railway  Air  Conditioning,  Industrial  Air  Conditioning, 
Piping  and  Duct  Insulation,  Electrical  Heating  and  Radiant  Heating. 

The  Catalog  Data  Section  of  the  GUIDE  is  receiving  more  recognition 
as  each  issue  appears  for  the  valuable  product  data  contained  therein. 
As  usual,  the  manufacturers  have  cooperated  in  accomplishing  the  dual 
purpose  of  this  part  of  the  GUIDE;  to  provide  authoritative  and  condensed 
catalog  information  for  the  Guide  user,  and  to  develop  an  effective  and 
productive  advertising  medium  for  the  manufacturer. 

In  offering  the  16th  edition  of  the  HEATING,  VENTILATING,  AIR  CON- 
DITIONING GUIDE,  the  Committee  wishes  to  acknowledge  not  only  the 
editorial  assistance  unselfishly  given  by  many  whose  aid  is  specifically 
accredited  elsewhere,  but  also  the  valuable  suggestions  offered  by  the  many 
readers  and  users  of  other  editions.  It  is  hoped  that  improvements 
and  additions  will  be  suggested  to  future  Committees  by  readers  of 
this  volume,  particularly,  as  perfection  is  not  of  human  attainment. 

Without  the  publication  of  previous  editions,  the  issuance  of  the 
HEATING,  VENTILATING,  AIR  CONDITIONING  GUIDE  1938  in  this  fairly 
complete  state  m  so  short  a  time  would  be  practically  impossible.  It  is 
the  Committee  s^hope  that  the  same  enthusiastic  reception*  given  to 
earlier  volumes  will  be  accorded  this  edition  of  15,500 


:V,  Chairman 

# 

GUIDE  PUBLICATION  COMMITTEE 


CONTENTS 


HEATING  •  VENTILATING  •  AIR  CONDITIONING  •  GUIDE  1938 

PAGE 

TITLE  PAGE i 

PREFACE.- ii 

CONTENTS iii-v 

EDITORIAL  ACKNOWLEDGMENT iv 

CODE  OF  ETHICS  FOR  ENGINEERS vi 

INDEX  TO  TECHNICAL  DATA vii 

TECHNICAL  DATA  SECTION 1-840 

CATALOG  DATA  SECTION 841-1162 

INDEX  TO  ADVERTISERS 843 

INDEX  TO  MODERN  EQUIPMENT „ 1165 

ROLL  OF  MEMBERSHIP. 1-80 

SECTION  I.   PRINCIPLES 

Chapter    1.  Air,  Water  and  Steam... 1 

Chapter    2.  Refrigerants  and  Air  Drying  Agents 35 

Chapter    3.  Physical  and  Physiological  Principles  of  Air  Conditioning....  51 

Chapter   4.  Air  Pollution... _ 79 

SECTION  II.   BASIC  DATA  AND  COMPUTATIONS 

Chapter    5.  Heat  Transmission  Coefficients  and  Tables..™ 89 

Chapter    6.  Air  Leakage. 121 

Chapter    7.  Heating  Load 133 

Chapter    8.  Cooling  Load 147 

SECTION  III.   COMBUSTION  AND  UTILIZATION  OF  FUELS 

Chapter    9.  Fuels  and  Combustion 165 

Chapter  10.  Chimneys  and  Draft  Calculations 179 

Chapter  11.  Automatic  Fuel  Burning  Equipment 201 

Chapter  12.  Heat  and  Fuel  Utilization 229 

SECTION  IV.   STEAM  AND  HOT  WATER  HEATING  SYSTEMS 

Chapter  13.  Heating  Boilers 243 

Chapter  14.  Radiators  and  Gravity  Converters... „ 263 

Chapter  15.  Steam  Heating  Systems 276 

Chapter  16.  Piping  for  Steam  Heating  Systems.- 301 

Chapter  17.  Hot  Water  Heating  Systems  and  Piping 331 

Chapter  18.  Pipe,  Fittings  and  Welding 35£ 

(Continued  on  Page  V) 


EDITORIAL  ACKNOWLEDGMENT 

T70R  16  years  the  HEATING,  VENTILATING,  AIR  CONDITIONING  GUIDE 
I/ has  been  published  by  the  AMERICAN  SOCIETY  OF  HEATING  AND 
VENTILATING  ENGINEERS  and  it  retains  its  leadership  asjthe  authoritative 
reference  volume  of  the  profession  and  its  allied  industries.  Its  users  are 
legion  and  they  have  adopted  The  Guide  as  their  standard  reference 
source  because  they  recognize  that  the  data  are  unbiased,  up-to-date  and 
readily  usable.  This  has  been  made  possible  because  of  the  willingness  of 
hundreds  of  technical  experts  to  contribute  freely  from  their  knowledge 
and  practical  experience  for  the  advancement  of  the  profession. 

To  the  following  individuals  the  Guide  Publication  Committee  is 
profoundly  grateful  for  their  assistance  in  the  production  of  the  1938 
edition,  and  also  to  those  former  contributors  who  have  previously 
prepared  a  firm  foundation  for  the  addition  of  new  material. 


H.  E.  ADAMS 
T.  N.  ADLAM 

.  C.  ALBRIGHT 

!.  L.  ALT 
0.  W.  ARMSPACH 
C.  L.  ARNOLD 
C.  M.  ASHLEY 
PROF.  LL.  BEAL 

F,  R.  BICHOWSKY 
J.  L.  BLACKSHAW 
M.  G.  BLUTH 

C.  A.  BOOTH 
C.  J.  BRAATZ 

C.  E.  BRONSON 
PROF.  A.  I.  BROWN 
C  A.  BULKELEY 
W.  H.  CARLTON 

P.  D.  CLOSE 
SABIN  CROCKER 
R.  C.  CROSS 

D.  N.  CROSTHWAIT,  JR. 
PHILIP  DRINKER 

G.  G.  EARLY,  JR. 

E.  V.  ERICKSON 
C.  E.  ERNST 
JOHN  EVERETTS,  JR. 
PROF.  M.  K.  FAHNESTOCK 
W.  L.  FLEISHER 

W.  G.  FRANK 
J.  E.  GODFREY 


C  D.  GRAHAM 
W.  A.  GRANT 

'.  R.  HERTZLER 

:.  G.  HILLIER 

F.  C.  HOUGHTEN 

PROF.  C.  M.  HUMPHREYS 

H.  F.  HUTZEL 

L.  P.  HYNES 

A.  J.  JOHNSON 

E.  F.  JONES 

C.  F.  KAYAN 

R.  T.  KERN 

R.  E.  KEYES 

PROF.  V.  O.  KNUDSEN 

PROF.  S.  KONZO 

PROF.  A.  P.  KRATZ 

PROF.  G.  L.  LARSON 

L.  L.  LEWIS 

S.  R.  LEWIS 

H.  A.  LOCKHART 

ARTHUR  MCCUTCHAN 

PROF.  L.  G.  MILLER 

PROF.  P.  E.  MOHN 

L.  L.  MUNIER 

,H.  C.  MURPHY 

PROF.  D.  W.  NELSON 

P.  NICHOLLS 

R.  F.  NORRIS 

A.  J.  OFFNER 

0.  W.  OTT 


k: 


:S.  PARKINSON 
.  G.  RAPPOLT 
PROF.  T.  F.  ROCKWELL 
J.  0.  Ross 

S.  I.  ROTTMAYER 

PROF.  F.  B.  ROWLEY 
.  S.  SANDFORT 

:OF.  W.  M.  SAWDON 
PROF.  L.  E.  SEELEY 
LESTER  SEELIG 
C.  G.  SEGELER 
A.  M.  SELVEY 

C.  D.  SHIELDS 
R.  W.  SHIELDS 
A.  L.  SIMISON 

D.  C.  SIMPSON 
T.  H.  SMOOT 

A.  E.  STAGEY,  JR. 
D.  J.  STEWART 
C.  A.  THINN 
R/  J.  THOMPSON 
W.  W.  TIMMIS 
PROF.  G.  L.  TUVE 

.  H.  VAN  ALSBURG 

'.  0.  URBAN 
A.  R.  WALKER 
J.  H.  WALKER 
PROF.  G.  B.  WILKES 

M.  S.  WUNDERLICH 

PROF.  C.  P.  YAGLOU 


The  members  of  the  Society  are  especially  indebted  to  these  engineers 
who  have  aided  in  the  preparation  of  this  volume  and  the  Guide  Publi- 
cation Committee  hereby  expresses  its  appreciation  for  the  loyal  coopera- 
tion of  the  many  contributors  to  this  16th  edition. 

GUIDE  PUBLICATION  COMMITTEE 
ALBERT  BUENGER,  Chairman 


S.  H.  DOWNS 
C.  H.  B.  HOTCHKISS 
E.  N.  MCDONNELL,  Advisory 


S.  S.  SANFORD 
W.  H.  SEVERNS 
JOHN  JAMES,  Technical  Assistant 


CONTENTS  (Concluded) 


SECTION  V.   AIR  SYSTEMS  PAGE 

Chapter  19.  Gravity  Warm  Air  Furnace  Systems 377 

Chapter  20.  Mechanical  Warm  Air  Furnace  Systems 393 

Chapter  21.  Central  Systems  for  Heating  and  Humidifying 409 

Chapter  22.  Central  Systems  for  Cooling  and  Dehumidifying 423 

Chapter  23.  Unit  Heaters,  Ventilators,  Air  Conditioning,  Cooling  Units 435 

Chapter  24.  Cooling  and  Dehumidification  Methods „ 469 

Chapter  25.  Spray  Equipment  for  Humidification  and  Dehumidification,.  499 

Chapter  26.  Air  Cleaning  Devices 519 

Chapter  27.  Fans 531 

Chapter  28.  Air  Distribution 547 

Chapter  29.  Air  Duct  Design.- 563 

Chapter  30.  Sound  Control 583 

SECTION  VI.   GENERAL 

Chapter  31.  Air  Conditioning  in  the  Treatment  of  Disease 597 

Chapter  32.  Railway  Air  Conditioning 60S 

Chapter  33.  Industrial  Air  Conditioning 62] 

Chapter  34.  Industrial  Exhaust  Systems 63c 

Chapter  35.  Drying  Systems 64' 

Chapter  36.  Natural  Ventilation.- 669 

Chapter  37.  Automatic  Control 683 

Chapter  38.  Motors  and  Controls 703 

Chapter  39.  Piping  and  Duct  Insulation 719 

Chapter  40.  Electrical  Heating 741 

Chapter  41.  Radiant  Heating 753 

Chapiei"  42    District  Heating™ 765 

Chapter  43.  Water  Supply  Piping  and  Water  Heating 783 

Chapter  44.  Test  Methods  and  Instruments.. 807 

Chapter  45.  Terminology 819 


CODE  of  ETfflCS  for  ENGINEERS 

ENGINEERING  work  has  become  an  increasingly  important  factor 
in  the  progress  of  civilization  and  in  the  welfare  of  the  community. 
The  engineering  profession  is  held  responsible  for  the  planning,  construc- 
tion and  operation  of  such  work  and  is  entitled  to  the  position  and 
authority  which  will  enable  it  to  discharge  this  responsibility  and  to 
render  effective  service  to  humanity. 

That  the  dignity  of  their  chosen  profession  may  be  maintained,  it  is 
the  duty  of  all  engineers  to  conduct  themselves  according  to  the  principles 
of  the  following  Code  of  Ethics: 

1 — The  engineer  will  cany  on  his  professional  work  in  a  spirit  of  fairness 
to  employees  and  contractors,  fidelity  to  clients  and  employers,  loyalty 
to  his  country  and  devotion  to  high  ideals  of  courtesy  and  personal 
honor. 

2-— He  will  refrain  from  associating  himself  with  or  allowing  the  use  of  his 
name  by  an  enterprise  of  questionable  character. 

3 — He  will  advertise  only  in  a  dignified  manner,  being  careful  to  avoid 
misleading  statements. 

4 — He  will  regard  as  confidential  any  information  obtained  by  him  as  to 
the  business  affairs  and  technical  methods  or  processes  of  a  client  or 
employer. 

5 — He  will  inform  a  client  or  employer  of  any  business  connections,  in- 
terests or  affiliations  which  might  influence  his  judgment  or  impair  the 
disinterested  quality  of  his  services. 

6 — He  will  refrain  from  using  any  improper  or  questionable  methods  of 
soliciting  professional  work  and  will  decline  to  pay  or  to  accept  com- 
missions for  securing  such  work. 

7 — He  will  accept  compensation,  financial  or  otherwise,  for  a  particular 
service,  from  one  source  only,  except  with  the  full  knowledge  and 
consent  of  all  interested  parties. 

8 — He  will  not  use  unfair  means  to  win  professional  advancement  or  to 
injure  the  chances  of  another  engineer  to  secure  and  hold  employment. 

9 — He  will  cooperate  in  upbuilding  the  engineering  profession  by  exchang- 
ing general  information  and  experience  with  his  fellow  engineers  and 
students  of  engineering  and  also  by  contributing  to  work  of  engineering 
societies,  schools  of  applied  science  and  the  technical  press. 

10— He  will  interest  himself  in  the  public  welfare  in  behalf  of  which  he  will 
be  ready  to  apply  his  special  knowledge,  skill  and  training  for  the  use 
and  benefit  of  mankind. 


INDEX 


HEATING  VENTILATING  Am  CONDITIONING 
GUIDE  1938 

Technical  Data  Section 
Chapters  1-45  and  Pages  1-840 


Abbreviations,  831 

Absolute  humidity,  8,  819 
Absolute  pressure,  807,  819 
Absolute  temperature,  819 
Absolute  zero,  819 
Absorption,  (sec  also  Regain) 
agents,  44 

as  means  of  dehumidification,  492 
by  building  materials,  155 
of  solar  radiation  by  glass,  152 
of  sound,  592 
system,  492,  493 
Acceleration,  819 

due  to  gravity,  819 
Acclimatization,  56 
Acoustics,  acoustical,  583 

treatment,  591 
Activated  alumina,  39 
Adiabatic  saturation,  11,  495,  502,  819 

driers,  649 

Adjustable  speed  motor,  704,  709,  710 
Adsorption,  819 
agents,  37 

as  means  of  dehumidification,  490 
systems 
alumina,  491 
silica  gel,  491 
Air 

adiabatic  saturation  of,  11 
amount  per  person,  70 
atmospheric,  1 
changes  of,  indoors,  51, 129 
cleaning  devices,  519,  819 
A.S.H.V.E.  code  for,  519 
requirements  of,  519 
types  of,  520 
composition  of,  1,  51 
density  of,  6 

distribution  of,  72,  397,  547 
balancing,  system,  560 
for  comfort,  69 
effect  of  turning  blades,  554 
factors  in  room  cooling,  552 
factors  in  room  heating,  554 
grille  locations,  547 
natural  ventilation,  669 
railway  air  conditioning,  560,  610 
residence,  397 

with  unit  air  conditioners,  455 
with  unit  heaters,  441 
with  unit  ventilators,  446 
dry,  1,  4,  8,  59,  822 
drying  agents,  35,  37 
ducts,  563,  (see  also  Ducts,  Air) 
excess,  168 
exfiltration,  121,  413 
filtration,  121,  180,  229,  413,  820 


Air  (continue<f) 
flow,  72,  77 

control,  principles  of,  675 

formulae,  563 

into  a  hood,  638 

loudness  chart,  556 

natural,  measurement  of,  678 

requirements,  676 

through  openings,  670,  675 
friction  of,  in  pipes,  567,  568 
impurities  in,  79,  676 

size  of,  80 
ionization  of,  75 
leakage,  121,  127 

minimum  outdoor,  requirements,  7S 
mixtures  with  water  vapor,  12 
moist,  68 
motion,  72,  74 

movement,  measurement  of,  811 
odors  in,  51 
optimum  conditions,  62 

indoors  in  summer,  68 
outlet  noises,  554 
outside,  introduced, 

fan  systems,  414 

through  cracks,  126,  129 

through  doors,  127 

unit  air  conditioners,  455 

unit  ventilators,  447 
pollution,  79 

abatement  of,  84 

effect  on  health,  83 
primary,  167 
properties  of,  3, 4 

for  combustion,  167, 176 

for  ventilation,  70,  609 
recirculation  of,  77 

fan  systems,  411,  417 

unit  ventilators,  447 
saturated,  1,  5, 10, 827 
secondary,  167 
space  conductances,  93 
speeds  to  convey  material,  642 
standard,  828 
summer,  conditions,  68 
still,  57 

synthetic  chart,  829 
velocity,  (see  Velocity,  Air) 
vitiation,  51 
volume,  12 
washer,  499,  820,  (see  also  Washer,  Air) 

operation  of,  690 

saturation  efficiency,  502 
weight  of,  6 

Air  conditioning  51,  503,  819,  (see  also  Air) 
air  change  per  occupant,  71 
chemical  factors,  55,  81 
comfort  chart,  63,  64 
in  disease  treatment,  597 


Vil 


HEATING   VENTILATING  AIR  CONDITIONING  GUIDE  1938 


Air  conditionin 


,  -V.»7 

with,  ice,  V,,<»} 


, 

tus  for,  .503 
automatic  control.  <»83 
exhaust  aystems,  t>33 
operation  cf,  485 
process  conditions,  G21 
unit  coolers,  449 

objective  of,  1 

physical  factors,  51 

redrcalation,  77,  411.  417,  447 

symbola,  836 

units,  451 

Algae  formations.  514 
Allergic  disorders,  004 

classification  of,  601 

treatment  cf, 
apparatus  for,  604 
limitations  in,  605 
Alternating  current  motor,  703 
Altitude.  1S3 

Alumina  system  of  adsorption,  30,  491 
Aluminum  foil,  94 
Aluminum  oxide,  39 
Ammonia,  35,  36,  511 
Anemometer,  812.  820 
Anesthesia,  597 

apparatus,  507 

effect  of,  598 

inflammability,  598 
Anthracite,  165,  169,  (see  also  Coal) 

stokers,  205 
Apartment  bouses, 

hot  water  supply  to,  797 

steam  consumption,  234 

stokers  suitable  for,  206 
Appendicitis,  599 
Artheritis,  607 
A.S.H.V.E.  Codes  and  Standards,  247.  281,  518, 

534.  680,  839 

A.S.M.E.  boiler  construction  code,  257 
Artificial  fever,  602 

conditions  for,  603 

diseases  treated,  603 

limits  for.  603 

production  of,  603 
Asbestos,  725 
Ash* 

cared  for  by  stokers,  201 

fly,  79 

Asphyxia,  605 
Asthma,  604,  605 
Atelectasis,  605 
Atmosphere,  standard,  807 
Atmospheric   steam   heating    system,    (see    also 

Steam  Heating  Systems) 
Atmospheric  water  cooling  apparatus,  507 

design  of,  510,  511 

efficiency  of,  512,  516 
Atomization, 

for  humidifying.  504 

of  02,  214 
Attic  fans.  464 

Automatic  control,  399,  608.  (see  also  Controls) 
Automatic  fuel  burning  equipment,  201 
Awnings,  156,  406 
Arm!  velocity  formula,  for  hoods,  637 


B 


Babcock's  formula  for  steam  flow,  301,  766 

Baby  care,  (see  Nurseries) 

Baffles,  595,  820 

Balancing  air  distribution  system,  560 


Barn  ventilation  679 
Barometer, 

aneroid.  808 

mercurial,  807 

Barometric  pressure,  183,  807 
Baudelot, 

chamber,  502 

cooler,  496 

Bends,  expansion,  362 
BET,  British  equivalent  temperature,  356 
Biochemical  reactions,  control  of,  628 
Bituminous  coal,  165,  171 
Blast,  820 
Blower,  blowers,  531,  (see  also  Fans) 

standard  test  code  for,  534 
Body, 

human,  surface  area,  71 

odors,  71 

Boiler,  boilers,  243,  820 

allowances,  252,  802 

A.S.H.V.E.  test  codes,  248,  840 

A.S.M.E.  construction  code,  258 

baffles,  395,  820 

capacity,  243,  442 

care  during  summer,  261 

cast-iron,  243 

cleaning,  260 

codes,  248 

combustion  rate,  244 

connections,  258,  316 

controls,  698 

conversion,  218,  256 

design  of,  246 

domestic  oil  burners,  218 

draft  loss  through,  189 

efficiency  of ,  247,  251  m 

for  electric  steam  heating,  745 

erection  of,  259 

fittings,  258 

gas-fired,  222,  245,  256 

grate  area,  255 

heat  transfer  rates,  247 

heating,  surface,  247,  820 

horsepower,  251,  820 

installation,  256.  259 

insulation.  261 

limitations,  257 

low  pressure,  construction  code,  258 

maintenance,  259 

oil  burners,  4,  218 

operation,  259 

output,  250 

performance  curves,  254 

pick  up,  252 

pipe  tax,  253 

ratings  of,  248,  249 

run  out  sizes,  319 

scale  in,  260 

selection  of,  251,  254,  255 

settings,  218,  246 
for  mechanical  stokers,  211 

special.  245 

steel,  243 

troubles  with,  260 

types  of,  240 

warming-up  allowance,  252,  254 

water  line,  258 
Boiling  point  of  water,  27 
Booster, 

coils,  411 

fans,  390,  426 
Booths,  spray,  640 
Bourdon  tube,  808 
Boyle's  law,  7 

Brake  horsepower,  heat  equivalent  of,  141 
Breeching,  draft  loss  through,  193 
Brine,  454,  483 

British  equivalent  temperature,  756 
British  thermal  unit,  820 
Building,  buildings, 

absorption  coefficients,  155 

air  velocities  in,  569 


ALPHABETICAL  INDEX  TO  TECHNICAL  DATA  SECTION 


Building,  buildings  (continued) 

classification,  for  district  heating,  777 

construction,  heat  transmission  of,  91,  97 

district  heating,  770 

fuel  requirements  of,  229 

hot  water  supply  to,  794,  797 

intermittently  cooled,  149 

intermittently  heated,  141 

load  factors,  240 

materials,  heat  transmission  of,  97 

noise  in,  5S7 

saving  of  steam  in  771 

steam  consumption,  234 

tall,  infiltration  in,  128 

water  supply  to,  783 
Burner,  burners, 

automatic  equipment,  201 

coal,  201 

conversion,  224 

gas,  221 

oil,  213 
By-pass  method,  425,  820 


Cabinets,  (see  Enclosures) 
Calorie,  820 
Calorific  values, 

coal,  166 

gas,  176 

oil,  174 

Capacitor  motor,  706 
Capillary  moisture,  651 
Carbon  dioxide,  36 

concentration  in  air,  72 

as  corrosion  agent,  374 

as  an  Index  of, 

combustion,  168,  176,  212,  220,  224 
draft  loss,  192 
odors,  52 

measurement  of  815 

as  a  refrigerant,  38 
Carbon  monoxide, 

in  air,  84 

in  garages,  681 

produced  by  gas,  224 

produced  by  oil  burners,  220 

produced  by  stokers,  212 
Carnot  cycle,  475 

Cattle,  heat  and  moisture  produced  by,  678 
Ceilings,  heat  transmission,  111 
Central  air  conditioning  systems,  423 

classification  of,  423 

cooling  cycle  control  for,  691 

design  of,  427 

location  of  apparatus,  428 

ratings  of,  429 

spray  type,  424 

zoning,  428 
Central  fan  heating  systems,  409,  688,  820 

computations  for  413 

design  of,  413 

electrical,  744 

heating  cycle  control  for,  688 

heating  requirements  of,  412 
Characteristics  of  motors,  708 
Charles*  law,  7 

Chemical  reactions,  control  of,  628 
Chimney,  chimneys,  179 

areas  of,  187,  189,  191 

characteristics,  182 

construction  of,  195 

effect,  129,  670,  672 

for  gas  heating,  196 

gas  temperature,  184 

performance,  186 

sizes,  187, 189, 191, 198 

Venturi,  180 


Chorea,  603 

Cleaners,  air,  (see  Air,  Cleaning  Devices) 

Clearance,  window  sash,  124 

Climatic  conditions,  138 

Coal,  (see  also  Anthracite,  Coke,  Lignite) 

air  speed  for  conveying,  642 

analysis  of,  165 

bituminous,  165, 171 

burning  rate  chart,  238 

calorific  value,  166 

classification  of,  165 

dust,  disposal  of,  79 

dustless,  172 

pulverized,  172 

semi-bituminous,  165,  172 

size  of,  169 
Coal  burning  systems, 

automatic  control  of,  699 

automatic  firing  equipment,  201 

boilers,  243 

combustion  rate,  394 

draft  required  for,  192 

fuel  requirements,  calculation,  230 

furnace  requirements,  395,  400 

hand-fired,  173 

stokers,  201 
Codes, 

A.S.H.V.E.  codes  and  standards,  839 

for  grinding,  polishing,  and  buffing  wheels,  636 

for  proportioning  warm  air  heating  plants,  222 

for  rating  air  conditioning  equipment,  435,  462 

for  use  of  refrigerants,  426 

Coefficients  of  heat  transmission,  (see  Heat  Trans- 
mission, Coefficients) 
Coils, 

booster,  411 

cooling,  406,  453 

evaporator,  406 

heating,  404,  411 

hot  water,  404 

pipe.  323 

preheater,  411 

radiator,  263 

reheater,  411 

steam,  411 

tempering,  411 
Coke.  166,  210,  411 

combustion  of,  172 
Cold,  effects  on  human  body,  55 
Collectors,  dust,  643 
Column  radiator,  821 
Combined  system, 

air  conditioning  equipment,  423 

central  fan,  409 
Combustion,  165  • 

air  required  for,  167,  168, 176 

constants,  659 

of  different  coals,  169, 171,  209 

in  driers,  655 

of  gas,  176,  224 

of  oil,  219 

rates  for  heating  boilers,  244 

smokeless,  247 

with  various  stokers,  209 
Comfort,  57 

chart,  64 

conditions  of,  147 

effective  temperature,  60,  61,  62 

heating  for.  753 

level,  267 

line,  63.  66,  821 

for  men  working,  66 

optimum  air  conditions  for,  62 

school  children,  65 

zone,  62,  821,  (see  also  Zone,  Comfort) 
Compensated  cooling  control,  693 
Composition  of  water,  27 
Compound  wound  motor,  703 
Compressed  air,  504 
Compressors,  470 

control  of,  701 

reversed  refrigeration  495,  749 

types  of,  471 


HEATING    VENTILATING  AIR  CONDITIONING   GUIDE  1938 


Condensation, 

4>n  balidin*  surface*,  1*1 
metew,  773 

prevention  of,  141,  734 
rate  in  radiators,  267 

return  pumps,  2tal 

in  steam  beating  systems,  275,  301 
Condenser,  48 1 

design  data,  481,  511 

performance  of,  481 

turbine,  507 

types  cf,  481 

water  temperatures,  511 
Conditioning  and  drying,  627,  (s«  also  Atr  Condt- 

tionint) 
Conductance,  90,  92,  821 

of  air  maces,  90,  93 

of  building  materials,  97 

of  insulation.  97,  723 

surf  ace.  92 
Conduction,  263,  821 

drying  by,  647 

beater.  742 

Conductivity,  90.  92.  821 
Conductor,  821 
Conduit,  707 

Constant  relative  humidity.  821 
Constant  speed  motor,  704,  70S,  709 
Constant  temperature  drier,  650 
Construction  code  for  low  pressure  boilers,  258 
Contours,  velocity,  637 
Control,  controls,  683  821 

of  air  conditioning  equipment.  485.  683,  688,  700 
combined  system,  688 
split  system.  689 

apparatus,  684 

automatic,  399.  683.  697.  698 
gas  burner.  698 
oil  burner,  698 
stoker,  699 

compensated  cooling.  693 

of  cooling;  units.  695 

domestic  hot  water,  700 

of  draft,  181 

of  electric  motors,  711 

electric  system,  686 

of  electrical  heating.  750 

of  fans,  541 

modulating,  687,  745 

moisture  content.  625 

of  natural  ventilation,  399,  673 

of  noise,  584 

of  ofl  burning;  equipment,  698 

pneumatic  system,  686 

positive  acting,  686 

pressure,  685 

railway  systems.  612,  613 

rate  of  biochemical  reactions  628 

rate  of  chemical  reaction,  628 

rate  of  crystallization,  629 
"     " "         "        quipment,  701 


of  refrigeration  equi 
compressor,  701 


vacuum,  701 
weft  water,  702 

of  regain,  624 

of  relative  humidity,  685 

residential,  systems,  699 

room,  687 

self-contained,  system.  686 

of  sound,  583 

of  steam  V^t*"g  gys^rns,  291 

of  temperature,  220,  683,  750 

types  of,  686 

wut.  220.683,  750 

of  vacuum  pomps,  295 

rone,  291,  688 
Convection,  821 
Gosmctor*,  263,  268,  821 

A^H.V.E*  code  for,  271 

connections  for,  322 

correction  rating  factors,  271 

design  of,  269 

drying  by.  649 


Convectors  (continued) 

gravity,  263 

heat  emission  by,  270 

heating  capacity.  270      . 

performance  characteristics,  270 

selection,  270 
Conversion  burners,  224 
Conversion  equations,  833 
Coolers, 

surface,  431 

types  of  483 

unit,  435,  449 
Cooling,  11,  24 

with  central  fan  heating  systems,  406,  423,  485 

design,  system.  407,  427 

effect,  10 

effective  temperatures  for,  68 

by  electric  refrigeration,  470.  749 

equipment,  design  of,  507 

evaporative,  423,  483,  501 

of  fluids,  511 

of  human  body,  147 

load,  147 

with  mechanical  warm  air  systems,  407 

methods,  406,  423,  469 

ponds,  512 

railway  air  conditioning,  411 

relative  humidities  for,  68 

spray,  469 

surface,  469 

towers,  482,  512 

units,  thermostatic  control,  695 

water,  507 
Copper  pipe,  356 

heaUoss,  721 
Corrosion, 

of  boilers,  261 

of  industrial  exhaust  systems,  645 
protective  materials,  646 

inhibitors,  375 

of  pipe,  374 

tester,  375 
Costs, 

of  attic  fans,  460 

of  district  heating  service,  778 

of  railway  air  conditioning,  617 

of  unit  conditioners,  464 
Crack,  window,  124 
Crystallization,  control  of,  629 
Cyclone  dust  collector,  643 


Dalton,  law  of  partial  pressures,  1 
Damper,  dampers, 

apparatus  which  operates,  683 

control,  673 

in  duct  systems,  398 

motors,  685 

types  of,  398 
Decibel,  583,  822 
Definitions,  68 
Defrosting  coils,  450 
Degree-day,  822 

base  temperature  for,  234 

methods  of  estimating  fuel  consumption,  231 

records  for  cities,  232 
Degrees,  perspiration,  73,  75 
Dehumidification,  11.  419,  469,  822 

by  absorption.  492 

by  adsorption,  490 

effective  temperatures  for,  66 

methods  of,  423,  453,  490 

by  refrigeration,  469 

relative  humidities  for,  68 
Dehumidifier,  dehumidifiers,  169 

alumina,  491 

in  central  air  conditioning  systems,  424 

in  industrial  air  conditioning,  503 

silica  gel,  491 

types  of,  453,  507 


ALPHABETICAL  INDEX  TO  TECHNICAL  DATA  SECTION 


Density,  3,  822 

of  air,  6 

of  saturated  vapor,  12 

specific,  3 

of  water,  27 
Dennatitus,  604 

Design  conditions  in  industrial  conditioning,  621 
Design  temperature, 

dry-bulb,  138,  147 

wet-bulb,  147,  511 
Dew-point,  822 

relation  to  relative  humidity,  9 

temperature,  2 
Diameter,    circular    equivalents    of    rectangular 

ducts,  572 
Diarrhea,  600,  601 

Dichlorodifluoromethane,  35,  40,  473,  511 
Diffuser,  822 
Diphtheria,  52 
Direct  current  motor,  703 
Direct-indirect  heating  unit,  822 
Direct  radiator,  822 
Direct  return  system,  332,  822 
Dirt  pockets,  328 
Disc  fans,  test  code  for,  524 
Disease  treatment, 

air  conditions  for,  599,  600,  603 

allergic  disorders,  604 

anesthesia,  597 

artificial  fever,  602 

classification  of  diseases,  602,  605 

diseases  treated,  52,  599,  600,  603,  604,  605,  607 

explosion  hazard,  597 

fever  therapy,  602 

filtering  in,  600 

hospital  air  conditioning,  597,  607 

nurseries,  600 

operating  rooms,  597 

oxygen  therapy,  605 

premature  infants,  600 

satisfactory  air  conditions,  599,  600.  603 

sterilization  of  air,  650 

ventilation  rates,  598,  602 

Distribution  of  air,  547,  (see  also  Air,  Distribution} 
District  heating,  765 

building  connections,  770 

conduits,  767 

economies  in,  770 

meters,  774,  775 

pipe,  (see  also  Piping} 
distribution,  765 
returns,  767 
sizing,  766 

rates,  778 

steam  consumption,  777 

tunnels,  769 

Diverter,  back  draft,  196 
Domestic  oil  burners,  215 
Domestic  stokers,  204 
Domestic  supply, 

hot  water,  747,  799 
control,  700 
load,  253 

water,  783 
Doors, 

air  leakage  through,  127 

coefficients  of  transmission  of,  117 

natural  ventilation  through,  672 
Down-feed  piping  systems,  (see  Steam  Healing 

Systems) 
Draft,  179 

available,  182, 186 

back,  diverter,  196 
dimensions,  196 

calculations,  179 

capacity,  181 

control,  181 

equation,  187 


Draft  (continued) 

mechanical,  180 

natural,  179 

requirements,  169 

theoretical,  182 
Drain  connections,  259 
Drawing,  symbols  for,  836 
Drip,  822 

Dripping  of  steam  pipes,  327 
Drum  driers,  648 
Dry  air,  822 

Dry-bulb  temperature,  (see  Temperature,  Dry-bulb) 
Dry  return,  823 
Driers,  648,  649 

adiabatic,  649 

agitated,  648 

batch,  648 

compartment,  648 

continuous,  648 

cylinder,  648 

design,  658 

drum,  648 

festoon,  648 

high  temperature,  663 

induction,  648 

intermittent,  648 

rotary,  648 

spray,  648 

tower,  648 

tunnel,  648 

vacuum,  648 
Drying,  627,  647,  (see  also  Regain) 

adiabatic  temperature,  649 

air  circulation  in,  653 

combustion,  655 

by  conduction,  649 

constant  temperature,  650 

by  convection,  649 

design,  658 

direct  contact,  649 

equipment  for,  653 

estimating  method,  665 

factors  influencing,  651 

gas  combustion  constants  for,  659 

high  temperature,  652,  663 

humidity  in,  652 

humidity  chart,  654,  655 

industrial,  627,  647 

low  temperature,  652 

mechanism  of,  650 

methods  of,  647 

moisture  in,  651 

omissions  in  the  cycle,  650 

by  radiation,  647 

rules  for,  652 

stages  of  moisture  diffusion,  650 
constant  rate  period,  650 
falling  rate  period,  650 

sun,  647 

temperature  in,  652 

time  of,  653 
materials,  656 

ventilation  phase,  661 
Duct,  ducts 

air,  398,  563 
design  of,  563 

equal  friction  method,  569,  575 
velocity  method,  569 

for  air  distribution,  547 

air  velocities  in,  401,  642 

circular  equivalents,  572 

construction  details,  580,  641 

'    '      of  duct  systems,  398,  569,  578,  634,  640, 


head,  822 

intensity  required,  167, 190 

losses,  190 
in  chimneys,  192 
through  fuel  bed,  190 


heat  loss  from,  732 
humidity  measurement  in,  814 
insulation  of,  719,  732 
lining  factor  for  sound,  592 
noise  transmission  through,  592 
pressure  loss  in,  564 

elbows,  564,  642 
for  recirculated  air,  381 
resistance,  643 
sheet  metal  for,  580,  642 


HEATING   VENTILATING  AIR  CONDITIONING  GUIDE  1938 


Duct,  ducts  •coxiinutft 

suca  of,  367,  571,  633 

temperature  lose  in,  415 

temperature  measurement  in,  809 

velocity  measurement  in,  811 
Duit,  7W,  823 

air  speeds  to  convey,  635,  642 

catching  devices,  So 

collectors,  643 

concentration  in  air,  82,  815 

counter,  SIo 

disposal  of,  SO 

Industrial  exhaust  systems,  633 

measurement  cf,  815 

Dynamic  equilibrium,  Carrier's  equation  for,  2 
Dynamic  head.  823 
Dysenterfa,  52 


E 


Eczema,  604 

EDR,  equivalent  direct  radiation,  828 
Effective  temperature,  (see  Temperature,  Effective) 
Ether,  81,  579 
Elbow,  elbows, 
design  of.  367, 398 
equivalents,  340 
Ion  of  pressure  in,  564 
resistance  in,  643 
sheet  metal  used  in,  641 
welding  of.  368 
Electric,  electrical, 
automatic,  control  system,  686 
central  fan  heating  systems*  744 
control,  motor,  703 
current,  as  corrosion  agent,  374 
heat  equivalent,  141, 160. 750 
heating,  741 
auxiliary,  749 
cost  of  .750 
of  hot  water,  747 
industrial,  748 
heaters,  742 
conduction,  742 
gravity  convection,  743 
radiant,  743 
heating  elements.  252,  742,  743 

with  unit  heaters,  743 
lamp  bulbs,  heat  from,  160 
motors,  703 
resistors,  742 

Eliminator  plates  and  baffles,  499 
Enthalpy,  22,  823 
Entropy,  473, 478,  823 

tables,  36,  38, 40,  42, 44 
Equations,  conversion,  833 

dynamic.  2 

hygroscopic,  626 
Equipment  noise,  586 
Equipment  room,  design  of,  591 
Equivalent,  equivalents, 

circular,  572 

direct  radiation,  304,  601, 828 

tiljow,  340 

evaporation,  251, 823 

heat,  823 

of  air  infiltration,  140 
of  brate  horsepower.  141 
electrical,  833 
mechanical,  826 

length  of  run,  305 

square  feet,  264 
Kitfimated  design  load,  823 
Estimated  marmiTTTn  load,  823 
Estimating  driers,  665 
Estimating  fuel  consumption,  229 
Etfaytene.  567 
Eupatheoecope,  762,  817 


Evaporation,  516 
equivalent,  251 
from  human  body,  54,  74 
from  water  pans,  268 
Evaporative  condensers,  483 
Evaporative  cooling,  423,  483,  495,  501 
Evaporators,  483 
Exfiltration,  121, 229,  413 
Exhaust  systems,  633 
classification  of,  633 
collectors,  643 

corrosion,  protection  against,  645 
design  procedure  for,  634 
ducts  for, 

construction  of,  641 
design  of.  640 
resistance  in,  643,  644 
efficiency  of,  645 
fans  for,  645 
filters  for,  644 
flexible,  640 
hoods  for,  637 
air  flow  in,  638 

axial  velocity  formula  for,  637 
chemical  laboratory,  640 
large  open,  639 
velocity  contours  in,  637 
industrial.  633 
lateral,  637 
motors  for,  645 
spray  booth,  640 
suction  requirements,  635 
velocity  requirements,  635,  642 
Expansion, 
of  joints,  315,  767 
of  pipe,  315,  359,  767 
in  steam  piping,  767 
tanks,  349 
Explosion  hazard, 
inflammability  of  gases,  81 
in  operating  rooms,  597 
Exposure  factors,  140 
Extended  heating  surface,  823 
Extended  surface  heating  unit,  823 


F 


Fan,  fans,  531 

A.S.H.V.E.  test  code  for,  534 
attic,  464 

booster,  equipment,  390,  426 
control  of,  541 
designation  of,  543 
drives,  arrangement  of,  542 
for  drying,  540 
for  dust  collecting,  541,  645 
dynamic  efficiency  of,  533 
efficiency  of,  533 
in  electrical  heaters,  744 
furnaces,  393 
for  gas-fired  furnaces,  222 
induced  draft,  180 
for  industrial  exhaust  systems,  645 
mechanical  draft,  180 
mechanical  efficiency  of,  533 
motive  power  of,  543,  706 

control  of,  703 

operating  characteristics,  180,  533 
operating  velocities.  539,  540 
performance  of,  531,  539 
quietness  of,  442 
ratings  of,  538 

selection  of,  396,  538,  541,  543,  645 
static  efficiency  of,  533 
system  characteristics,  537 
systems  of  heating,  409 
tip  speeds,  538 
total  efficiency  of,  533 
types  of,  393,  531,  535,  539 
in  unit  conditioners,  455 
in  warm  air  systems,  390,  396 


ALPHABETICAL  INDEX  TO  TECHNICAL  DATA  SECTION 


Fatigue*  human,  56 

Fever  therapy,  (see  Artificial  Fever) 

Filter,  filters,  521 

automatic,  523 

cloth,  644 

design  of,  521 

dry  air,  524 

hay  fever  air,  604 

installation  of,  525 

resistance  of,  396 

for  sound,  392 

unit  type,  521 

viscous  type,  521 
Fire  walls,  640 
Firing  rate,  169, 171 
Fittings,  355,  (see  also  Connections,  Pipe) 

areas  of,  364 

boiler,  258 

copper,  365 

flanged,  366,  723 

lift,  287 

screwed,  364 

welding,  366,  370 
Flame,  with  oil  burners,  214,  219 
Flanges,  welding  neck,  371,  372 

Flexible  materials,  589 
Floors,  heat  transmission  through,  111 
~~         is  analysis,  816 
fluids, 
of,  511 

for  flow  of,  563 
774 

moisture  of,  626 


gages, 


Force,  824 

Forced-air  heating  system,  design,  3 

Forge  shops,  heat  given  off  in,  675 

Formulae, 

conversion,  833 

heat  transmission,  91 
Foundries,  heat  given  off  in,  675 


of  cooling  water,  517 

insulation  against,  733 
Friction, 

of  air,  in  pipes,  566,  567 

in  chimneys,  185 

coefficients,  567 

factors,  393 

heads  in  pipes,  336 

in  heating  units,  412 

losses  in  ducts,  565,  567,  571 

in  water  pipes,  791 

Fuel,  fuels,  165,  (see  also  Anthracite,  Coal,  Coke, 
Gas,  Lignite.  Oil) 

bed.  draft  loss  through,  189 

burning  equipment,  automatic,  201 

burning  rate  charts,  238 

consumption.  229,  236 

oil  gages,  221 

oil,  heating  value,  174,  660 

oil  specifications,  174 

requirements, 
of  buildings,  236 
degree-day  method.  231 
theoretical  method,  230 

utilization  of,  229 
Fumes,  79,  824 

industrial  exhaust  systems,  633 

toxicity  of,  83 

Fundamentals  of  heating  and  air  conditioning,  1 
Furnace,  furnaces,  824 

capacity,  383 

design  of,  173,  211,  246,  377,  383.  394, 400 

door  slot  openings,  486 

gas-fired,  222 

hand-fired,  173 

performance  curves  of,  385 

types  of,  221,  393,  403 

volume,  824 

for  warm  air  systems,  393 
Furnacestat,  399 


fuel  oil,  221 

pressure,  824 

steam,  258 

vacuum,  808 
Galvanometer,  809 
Garage,  garages, 

air  flow  necessary  in,  676 

A.S.H.V.E.  ventilation  code,  679 

heaters,  for,  224 
Gas,  gases, 

burner  control,  698 

burning  rate  chart,  239 

calorific  value.  141,  176 
hi  chimneys,  183 

combustion  constants,  659 

constant  for  dry  air,  8 

flue,  analysis,  816 

fuel, 

manufactured.  176 
natural,  176 
properties  of,  176 

inflammability,  81 

requirements  per  degree  day,  237 

scrubbers,  86 

toxicity  of,  83 
Gas-fired  appliances,  221 

automatic  control  of,  225,  698 

boilers,  222,  245,  456 

carbon  monoxide  produced  by,  224 

chimneys  for,  196 

classification,  221 

combustion  in,  224 

conditioning  unit,  462 

control  of,  225,  698 

conversion  burners,  224 

furnace  requirements  for,  394,  900 

heat  from,  160 

rate  of  gas  consumption,  395 

ratings  of,  226 

sizing,  225 

types  of  space  heaters,  223 

used  with  unit  heaters,  443 

warm  air  furnaces,  222 
Gaskets,  366 
Glass, 

heat  transmitted  through.  117,  152 

solar  radiation  through,  152 
Globe  thermometer,  762 
Glossary  of  terms,  819 
Goitre,  599 
Gonorrhea,  603 
Grates,  824 

areas  of,  249,  255,  383,  402,  421,  824 

of  furnaces,  249,  255,  383,  402,  421 

of  stokers,  201 
Gravity, 

circulation,  345 

converters,  263,  743 
heat  emission  of,  263 

gravity-indirect  heating  systems,  272 

pressure  heads,  344 

specific,  3 

steam   heating   systems,  275,    (see   also   Steam 
Heating  Systems) 

warm  air  heating  systems,  design  of,  377 
Grille,  grilles,  824,  (see  also  Registers) 

anemometer  readings  through,  812 

for  concealed  heaters,  270 

redrculating,  381 

of  roof  ventilators,  672 

velocity  through,  401 

for  warm  air  systems,  381,  397 


Hartford  return  connection,  258,  278,  318 

Hay  fever,  604 

Hazard  of  explosion,  in  operating  rooms,  597 


HEATING   VEWTILATINO  AIR  CONDITIONING  GUIDE  1938 


Health.  Sd,  8!M»,  f  see  also  Disease  Treatment) 
Heart  trouble,  605 
Heat,  824 

absorbed  by  bonding  structure,  141 
of  adsorption.  43  f     M 

air  infiltration  equivalent  of,  130 
capacity,  155,  823 

of  leader  pipe*,  378 
of  condensation,  45 
conduction,  821 
consumption,  224 
content, 

of  air  and  water  vapor.  2 

of  coal,  166 

of  dry  air.  22 

of  gase*,  661 

of  saturated  water  vapor,  23 
convection,  821 
conversion  equations,  833 
demand,  factors  governing,  133,  241 
effects  on  human  body,  54 
electrical  equivalents  of,  750,  834 

of  convectors,  263,  270 

by  radiation,  756 

of  radiators,  263,  270 
equivalent,  equivalents,  834 

of  air  infiltration,  130 

of  brake  horsepower.  140 

electrical,  350.  834 
exchanger.  507.  506 

shell  and  tube,  481 
flow  meter,  817 
gain* 

from  fixtures  and  machinery,  160 

for  insulated  pipe,  735 

from  outside  air,  158 

to  be  removed.  430 
infiltration  equivalent  of,  130 
latent,  31,  828, 

loss,  73,  76 
of  the  liquid,  28,  825 
loss, 

from  bare  pipe,  719,  721 

computation  of,  S9,  142,  750.  758 

cost  of.  720 

determination  of,  133, 140,  229,  753 

from  ducts,  730 

effect  of  insulation  on,  737 

from  human  body,  73,  753,  755 

by  infiltration,  130,  229 

latent,  73,  76 

from  piping  of  gas-fired  furnaces,  225 

by  radiation,  61,  753 

sensible,  73.  755 

to  unbeated  rooms,  118 

•vtvntjfaf \nf\i  675 

mftTftTiiyp^  probable  demand,  133,  241 

of  mixing.  47 

Tru^f^r^fg]  eQuivalent  of,  826 
produced  by  cattle,  679 
produced  by  human  body,  53 
pump,  472,  749 
radiant,  753 

calculation  of,  758 

measurement  of,  761 

types  of.  756 
radiation,  743.  753 
regulation  in  p*?",  53,  57 
requirements,  229 
sensible,  147.  827 

of  air,  12 

loss,  73,  756 

of  water,  31 
solar,  151 
sources  of,  745,  754 

other  than  heating  plant,  140,  149 
specific,  31 
total,  22.  829 

of  saturated  steam,  28 
transfer,  89 

coefficients,  90 

rate,  247 


Heat  (continued) 
transmission,  89,  754 
through  air  spaces,  91 
through  building  materials,  91 
calculations,  89 
coefficients,  89,  96 
of  ceilings,  111 
combined,  118 
of  copper  pipe,  721 
of  doors,  117 
of  floors.  111 
of  glass  walls,  117 
of  insulation,  97,  821 
of  partition  walls,  110 
of  roofs,  114 
of  skylights,  117 
of  surface  conductance,  92 
of  walls,  104 
of  windows,  117,  151 
convection  equation,  754 
definition  of  terms  used,  90 
effects  of  solar  radiation  on,  151 
formulae,  91 
through  glass,  116,  151 
measurement  of,  817 
in  surface  coolers,  431 
by  surfaces  not  exposed  to  the  sun,  149 
symbols  used  in  formulae,  90 
tables,  89,  97 
through  ducts,  730 
time  lag,  155 
utilization,  229 
Heaters, 
direct-fired,  443 
for  domestic  hot  water,  799 
electric,  741 
capacity  of,  750 
conduction,  743 
convection,  743 
radiant,  223.  743 
space,  223 
unit.  437,  743 
wall,  222 

Heating,  (see  also  Heaf) 
auxiliary,  749 
district,  765 
effect  of  radiators,  266 
electrical,  741 
elements,  electric,  742 
fundamentals  of,  1 
load,  133 
medium,  825 
radiant,  743,  753 
railway  air  conditioning,  611 
by  reversed  refrigeration,  472,  749 
surface,  247,  825 

square  foot  of,  828 
symbols,  836 
systems, 
district,  765 
electrical,  741 
fan,  409 

gravity  warm  air  furnace,  377 
hot  water,  331,  825 
mechanical  warm  air  furnace,  393 
radiant,  743,  753 
steam,  275,  745 
units, 

blow-through,  411 
central  fan,  744 
draw-through,  411 
value,  fuel  oil,  660 
water,  783 

Henry  and  Dalton,  law  of,  375 
Hoods, 

axial  velocity  formula,  637 
canopy,  639 

for  chemical  laboratories.  640 
design  of,  634 
for  exhaust  systems.  637 
of  furnaces,  395    • 
open,  639 

suction  pressures  at,  635 
velocity  pressures  at,  637 


ALPHABETICAL  INDEX  TO  TECHNICAL  DATA  SECTION 


Horsepower,  825 
boiler,  251 

brake,  heat  equivalent  of,  140 
Hospital  air  conditioning,   (sec  Disease  Treat- 
ment) 

Hot  box,  817 
Hot  plate,  817 
Hot  water,  domestic 
control  of,  700 
load,  253 
'     supply,  797 
Hot  water  heaters,  245,  799 
Hot  water  heating  systems,  331,  825 
electric,  720 

forced  circulation,  331,  337 
gravity  circulation,  331 
installation  of,  351 
mechanical  circulation,  333 
Hot  water  piping,  331 
Hotels, 

steam  consumption,  234 
stokers  suitable  for,  201 
temperatures  of,  in  winter,  134 
water  supply,  783 
Humidificatfon,  10,  499,  825 
apparatus  for,  503 
atomization  for,  504 
effective  temperatures  for,  65 
methods  of,  452 
relative  humidities  for,  68 
for  residences,  403 
systems  of,  503 
with  washer,  501 
Humidifier,  humidifiers,  466 
atomizing,  504 
with  fan  systems,  419 
high-duty,  504 
self-contained,  505 
spray,  505 
types  of,  466,  503 
Humidistat,  400,  825 
Humidity,  8,  825 
absolute,  8,  819 
control,  685 

railway  air  conditioning,  612 
in  drying,  652 
in  hospitals,  597 

for  industrial  processing,  622,  623 
measurement  of,  814 
optimum,  68 

relative,  9,  827,  (see  also  Relative  Humidity) 
in  comfort  zone,  63 
effect  on  moisture  regain,  625 
relation  to  dew-point,  9 
specific,  8,  825 
Hygroscopic  materials,  626 
moisture  content,  625 
processing  of,  627 
regain,  626 
Hygrostat,  825 
Hypertension,  607 
Hyperthyroidism,  607,  699 


Ice,  in  air  conditioning,  407,  454,  496 

control  of,  701 
Inch  of  water,  825 

Induction  motor,  707,  710,  (see  also  Motors) 
Industrial, 
air  conditioning,  621 
apparatus  for,  449,  503 
calculations,  629 
air  pollution,  79 
control, 

biochemical  reactions,  628 
chemical  reactions,  628 
crystallization,  629 
moisture  content,  625 
of  regain,  624 


Industrial  (continued) 

cooling  systems,  469 

design  conditions,  621 
drying,  540,  627 

electrical  heating  systems,  748 

exhaust  systems,  633,  (see  also  Exhaust  Systems) 

general  requirements,  624 

heat  sources,  141 

temperatures  and  humidities  for  processing,  622, 
623 

unit  heaters,  444 
Infants,  premature,  63,  65,  600 
Infiltration,  121 

average,  126 

fuel  utilization,  229 

heat  equivalent,  130 

through  shingles,  123 

through  walls,  122 

through  windows,  124 
Inflammability  of  gases,  81 
Institutions,  water  supply  to,  804 
Instruments,  807 
[nsulation,  825 

asbestos  type, 

corrugated,  725,  726 
laminated,  727,  728 

of  boilers,  261 

bright  metal  foil,  94,  95 

building,  751 

characteristics  of,  97,  723 

of  conduits,  738 

of  ducts,  732 

economical  thickness,  736 

with  electrical  heating,  715 

heat  transmission  through,  97,  723 

for  low  temperatures,  733 

magnesia  type,  724 

of  piping,  719 

to  prevent  condensation,  141,  734 

to  prevent  freezing,  733 

reflective  type,  94,  95 

rock  wool  type,  729 

of  sound,  587 

tables,  97,  724 

thickness  needed,  736 
underground,  737 
of  vibration,  587 
lonization  of  air,  75 
Isobaric,  825 
Isothermal,  7,  826 


J-K 


Joints,  expansion,  315,  767 
Kata  thermometer,  811 


Lag  in  heat  transmission,  155 
Latent  heat,  31,  826 

loss,  72 

of  water  vapor,  12 
Lateral  exhaust  system,  637 
Leader  pipes,  378 

heat  carrying  capacity  of,  379 

size  of,  379,  389 

Leakage  of  air,  121,  (see  also  Infiltration) 
Lignite,  166 

Liquid,  heat  of  the,  28,  825 

Lithium  chloride  system  of  adsorption,  46,  492,  493 
Load, 

building  factors,  240 

cooling,  147 

design,  251,  823 

heating,  133 

hot  water  supply,  825 

maximum,  824 

radiation,  824 
Low  temperature  insulation,  733 


XV 


HEATING    VENTHATINO  AIR  CONDITIONING   GUIDE  1938 


M 


Machinery, 

as  heat  scarce.  140,  159 
mountings  vibration,  587 
sound  insulation  of,  587 
Magnesia  insulation,  724 
Manometer,  811,  826 
Manual  control,  (see  Controls') 
Masonry  materials,  heat  transmission  through,  97 
Mass.  826 
Mb,  331,  826 
Mbh,  331,  820 

Mean  radiant  temperature,  754,  758 
Mechanical, 
draft  towers,  515 
equivalent  of  heat.  82G,  834 
fuel  burning  equipment,  201 
refrigeration,  35 
ventilation,  77 

warm  air  furnace  systems,  391 
air  distribution,  397 
design  of,  400 

register  and  grille  locations,  397 
Medical  treatment,  (see  Diseases) 
Mental  trouble,  605 
Mercurial  thermometer,  809 
Metabolism,  53,  73 
Meters, 
choice  of  .774 
condensation,  771 
fluid.  774 

NichoUs  heat  flow,  817 
steam  flow,  776 
types  of,  774 
water,  disc,  789 
Methyl  chloride,  37,  42,  511 
Metric  units,  835 
Micromanometers,  808 
Micron,  79.  826 

Mixture,  air  and  water  vapor,  12 
Modulating  control,  687 
Moisture, 
content, 

of  air,  72, 147.  503,  625 
capillary  or  free,  651 
of  hygroscopic  materials,  626,  651 
loss  by  human  body,  76 
from  outside  air,  158 
produced  by  cattle,  679 
regain.  fi9o> 
Mol,  826 

Monitor  openings,  672 
Monofluorotxichloromethane,  37,  44 
Motive  power.  703 
Motors,  electric,  703 
adjustable  speed.  704,  709 
adjustable  varying  speed,  704 
alternating  current,  705 
application  of,  708 
capacitor  type,  706 
characteristics  of,  708 
classification  of,  708 
compound  round,  703 
constant  speed,  704,  708 
control  equipment  for,  711 
automatic,  712 
manual,  711 
multispeed,  714 
pflot,  712 
single  phase,  716 
slip  ring,  715 
damper,  685 
direct  current,  703 
control  of,  713 

speed  characteristics,  704,  708 
as  heat  source,  159 
induction, 

automatic  start,  710 
capacitor  start,  706 
repulsion,  705 
repulsion  start,  707 
slip;ring  -wound  rotor,  710 
sQuirrd  cage,  707 


Motors,  electric  (continued) 

polyphase,  707 

selection  of,  645 

series  wound,  703 

shunt  wound,  703 

single  phase.  706 

special  applications,  711 

split  phase,  707 

synchronous,  711 

varying  speed,  705 
MRT,  mean  radiant  temperature,  754,  758 


N 

Natural  draft  towers,  515 
Natural  ventilation,  72,  669 
Nervous  instability,  607 
Neurosyphilis,  603 
Nicholls  heat  flow  meter,  817 
Noise,  (see  also  Sound) 
air  outlet,  554 
in  buildings,  584,  587 
control  of,  584 
through  ducts,  592 
through  room  wall  surface,  591 
with  warm  air  systems,  396 
equipment,  586 
kinds  of,  586 
level, 

acceptable,  585 
of  compressors,  471 
of  fans,  539 
of  unit  heaters,  442 
measurement  of  584 
through  building  construction  587 
Nozzle,  499 
air  spray,  499 
oil  atomizer,  214 
water  spray,  499 
Nurseries,  600 
equipment  for,  602 
requirements  for,  601 
ventilation  rate,  602 


Odors,  69 

of  human  origin,  51 

concentration  70 

removed  by  outside  air,  71 
Off  peak  heating,  748 
Oil,  oils, 

atomization  of,  507 
burner,  burners, 

air  for  combustion,  214 

air  supply  for,  214,  219 

boilers,  216.  218 

burning  rate  chart,  238 

classification,  215 

combustion,  218 

for  commercial  use,  216 

control  of,  220,  698 

design  considerations,  219 

for  domestic  use,  classification,  214 

efficiency  of  combustion,  220 

flame  with,  214 

furnace  requirements,  246,  394 

ignition,  214 

oil  consumption,  229,  238 

operation,  214 

Orsat  test,  220 

specifications,  173 

types  of,  215 
calorific  value  of,  174 
classifications,  171 
as  corrosion  inhibitor,  375 
cost  of,  175 
gages,  221 
ignition  of,  174,  214 
preheating,  217 
specifications,  174 


ALPHABETICAL  INDEX  TO  TECHNICAL  DATA  SECTION 


One-pipe  steam  heating  systems,  275,  826 

Steam  Heating  Systems) 
Openings,  670 
air  inlet,  672 
monitor,  672      .     . 
for  natural  ventilation, 
location  of,  675 
resistance  offered  to  flow,  676 
size  of,  669 
types  of,  670 
Operating  rooms, 
Anesthesia,  597 
explosion  hazard,  597 
humidification,  598 
static  electricity,  598 
ventilation.  598 
Orifice,  orifices, 
friction  heads,  612 


seam, 
Orsat  test  apparatus,  212,  220,  224,  816 
Outlets,  (see  also  Registers,  Grilles') 

design  and  location  of,  559 
Oxygen,  375,  559 
Oxygen  therapy, 

diseases  treated,  605 

oxygen  chambers,  606 

oxygen  tents,  605 
Ozone,  77 


Paint, 

effect  on  radiators,  265 

soray  booths,  640 

temperatures  and  humidities  for  processing,  623 
Panel  radiation,  826 
Panel  warming,  827 
Partial  pressures,  Dalton's  law  of,  1 
Perspiration,  51,  54,  73,  75 
Petterson-Palmauist  apparatus,  815 
Pipe,  piping,  355 

bare,  heat  loss  from,  719 

bends,  315,  362 

capacities,  (see  Pipe,  Sizes) 

coil  radiators,  263 

conduit,  738,  767 

connections,  316,  770,  (see  also  Connections) 

copper,  356 

corrosion,  of,  374 

district  steam,  765  . 

dimensions  of,  359  (see  also  Pipe  Sizes) 

expansion  of,  315,  359,  767 

fittings,  364,  (see  also  Connections,  Fittings) 
for  water  supply,  788 
welding  fittings,  366 

flanges,  370,  723 

flexibility  of,  359 

freezing, 

prevention  of,  733 

friction,  791 

of  air  in,  566,  567 
heads  in,  336 

gaskets,  366 

hangers,  364 

heat  loss  from  225,  719 

for  hot  water  heating  systems,  331,  351 

insulation  of,  719 

joints,  315,  769 

leaders,  378 

radiating  surface,  722 

radiators,  263 

refrigerant,  484 

scale  in,  374 

sizes, 

for  boiler  runouts,  318,  766 

for  central  fan  systems,  323 

for  convector  connections,  322 

dimensions,  356,  359 

for  district  heating,  766 

for  domestic  hot  water,  795 


Pipe,  piping,  sizes  (continued) 
elbow  equivalents,  340 
equivalent  length  of  run,  305 
friction  head,  337,  791 

of  orifices  in  unions,  343 
for  Hartford  return  connection,  318 
for  hot  water  heating  systems,  335 
for  black  iron,  337,  338 
for  copper  tube,  337,  339 
forced  circulation  systems,  337 
gravity  circulation  systems,  345 
for  indirect  heating  units,  325 
mains,  790 

for  pipe  coil  connections,  323 
for  radiator  connections,  320 
refrigerant,  484,  486 
return,  capacity  of,  308.  767 
steam,  302,  306,  307 
underground,  767 
tables.  306,  655 
tees,  364 

for  underground  steam,  767 
for  water  supply,  787 
weights,  361 
steam,  capacity  of,  304 
for  steam  heating  systems,  275,  301,  (see  also 

Steam  Heating  Systems) 
supports,  364 
sweating,  734 
tax,  253 

tees,  dimensions  of,  367 
threads,  363,  365 
tunnels,  767 
types  of,  355 
underground, 
insulation  of,  737 
steam,  767 
for  unit  heaters,  442 
valves,  370 
water  supply,  783 
weights  of,  356 
welding,  366 

Pitot  tube,  811  .    .       .         .    im 

Plastering  materials,  heat  transmission  through,  101 
Plenum, 

chamber,  827  nnn 

systems,  automatic  control  of,  688 
Plumbing  fixtures,  377 
Pneumatic  control  system,  286 
Pneumonia,  52,  599,  605,  607 
Pollen,  605 
Pollution  of  air,  83 
Polyphase  motors,  707 
Ponds,  cooling,  512 
Positive  acting  control,  686 
Post-operative  pneumonia,  599 
Potassium  permanganate,  514 
Potentiometer,  827 
Power,  827 

conversion  equations,  833 
electric,  750 
supply  for  controls,  686 

Precipitators,  dust,  527 
Premature  infants,  600 

humidity  of,  601 

mortality  of,  602 

requirements  of,  601 
Pressure,  pressures, 

absolute,  819 

air 

in  heating  unit,  412 
measurement  of,  811 

atmospheric,  807,  820 

for  atomization,  504 

automatic  control,  685 

barometric,  183,  807 

basic,  3 

controllers,  685 

conversion  equations,  833 

drop,  566,  791 

drop  through  refrigerant  pipe,  486 

dynamic.  823 


loss  throug 


r  pipe,  339,  486 
ducts,  563,  643 


HEATING    VENTILATING   AIR  CONDITIONING   GUIDE  1938 


Pressure,  pressure  \.& 


i  , 

jurtial,  Da  I  ton*  a  law  of,  1 
rcfnxeratintf  piant,  4S*t> 
of  saturated  vapor,  12 
static,  421,  82$ 
steam, 

in  direct  beating,  760 
drop,  278,  302,  307 
initial,  302 

in  oriiice  systems,  290 
saturated,  28 

in  sub-atmospheric  systems,  2S9 
total,  829 
vapor,  31,  830 
velocity,  83O 
water,  27,  789 
Prime  surface,  827 
Processing,  621 

cooling  systems,  469,  621  . 

industrial,  temperatures  and  humidities  for,  622 
of  textiles,  626 
unit  heaters,  444 
Propeller  fans,  test  code  for,  534 
Psychrometer,  827 

sling,  811 
Psycfarometric, 
chart,  25,  60,  61,  62,  (back  ewer) 
for  drier,  654 
explanation,  25 
tests,  59 

Pulmonary  disturbances,  605 
Pump,  pumps, 
centrifugal,  334 
characteristics,  181 
circulating,  333 
condensation  return,  292 
heat,  472,  749 
vacuum,  293 
Pyrometer,  810,  827 
mercurial.  810 
optical,  810 
radiation,  810 
thermo-electric,  S10 


0-R 

Quality, 

of  air,  69, 70, 71 

impaired  by  rerirculation  83 
Quantity, 

of  air, 

measurement  of,  811 

necessary  for  ventilation,  70.  71,  72,  158, 
609,  675 

of  cooling  water,  511 
Radiant  heaters,  743 
Radiant  heating,  753 

physical  and  physiological  factors,  753 
Radiation,  827 

by  black  body,  759 

drying  with,  647 

equivalent  direct,  304, 828 

heat  loss  by,  63,  76,  754 

by  human  body,  63,  76,  754 

load,  252 

ofjwpe,722 

by  radiators,  263 

solar.  151,  (see  also  Solar  Heat) 
occlusion  of ,  84 
through  glass,  152 
through  walls,  152 

ultra-violet.  75, 82 
Radiator,  radiators,  263,  827 

A^,H.V.E.  code  for,  271 

column,  821 

concealed,  821 

condensation  rate  in,  267 

connections.  320, 348 

control  of,  687 

correction  rating  factors,  271 

effect  of  saperheated  steam,  265 

enclosed,  267 

gas-fired,  223 


Radiator,  radiators  (continued) 
heat  emission  of,  263,  270 
heating  capacity  of,  270 
heating  effect  of,  266 
for  hot  water  systems,  346 
output  of,  264 
paint,  effect  of,  265 
panel,  827 
pipe  coil,  203 
ratings  of,  264 
recessed,  827 
selection,  270 
tube,  829 
types  of,  263 
wall,  output,  264 
warm  air,  223 

Railway  air  conditioning,  609 
air  distribution,  560,  610 
cleaning,  611 
cooling  equipment,  611 

calculation  of,  load,  619 

capacity,  612 
costs,  617 
heating,  611 
humidity  control,  612 
power  requirements,  613 

tractive  resistance,  615 
temperature  control,  613 
ventilation,  609 
Raoults  law,  493 
Receivers,  alternating,  299 
Refrigerants,  35,  827 
ammonia,  36 
carbon  dioxide,  38 
codes  for  use  of,  426 
dichlorodifluoromethane,  40 
lithium  chloride,  46,  47 
methyl  chloride,  42 
monofluorotrichlorometbane,  44 
water,  45 

Refrigerating,  capacity,  429,  475 
Refrigerating  plant,  24,  469 
centrifugal,  478 
compressor,  470,  512 
operating  methods,  485 
size  of,  429,  475.  485 
steam  jet  system,  477,  512 
types  of,  471 
Refrigeration, 
characteristics,  481 

curves,  480,  481 
coefficient  of  performance,  475 

carnot  cycle,  475 
compression  ratio,  477 
control  of,  equipment,  701 
dehumidification  by,  470 
efficiency, 

cycle,  475 

ejector,  479 

mechanical,  477   . 
losses.  476 
mechanical,  472 
pipe  sizing,  484 

discharge,  486 

liquid,  487 

suction,  488 
practical  cycle,  475 
reverse  cycle,  749 

limiting  factors,  749 
systems, 

absorption,  dosed,  493 

centrifugal,  479 

mechanical,  496 

steam  ejector,  477 

various  types,  469 
theoretical  mechanical  cycle,  473 
theoretical  work  per  pound,  474 
ton  of,  429,  475,  829 
ton  days  of,  829 
unit  of,  429,  475 
Regain, 
control  of,  624 
of  hygroscopic  materials,  626 
Registers,  827,  (see  also  Grilles) 
with  gas-fired  furnaces,  223 
with  gravity  furnace  systems,  381 


ALPHABETICAL  INDEX  TO  TECHNICAL  DATA  SECTION 


Registers  (.continued')          . 
with  mechanical  warm  air  furnace  systems,  397 
selection  of,  381 
sizes,  381,  389 
temperature,  401 
velocity  through,  401 
Reheater,  424,  432 
Relative  humidity,  9,  826 
apparatus  sensitive  to,  684 
in  comfort  zone,  64,  68 

relation  of  dew-point  to,  9 
control  of,  684 
in  industrial  plants,  622,  624 
for  processing,  622 
in  public  buildings,  67 
in  residences,  403 
from  water  pans,  403 
Relays,  685 
Relief  valves,  350 
Repulsion  motors,  706,  707 
Research  residence,  388,  406 
Residences, 

air  distribution  in,  397 
automatic  fuel  burning  equipment,  201 
conditioning  units,  291,  460 
control  systems,  399,  699 
gas  heat,  221 
humidification  of,  403 
oil  burners  for,  213 
requirements  in,  405 
steam  consumption,  234 
stokers  for,  204 
Resistance, 

of  bright  metallic  surfaces,  94 
of  building  materials,  97 
in  ducts,  565,  643 
of  exhaust  systems,  643 
of  niters,  396 
of  insulators,  97 
thermal,  829 
thermometer,  810 
Resistor,  742 
Respiratory  diseases,  607 
Restaurants, 
tobacco  smoke,  in,  70 
water  supply  to,  804 
Return, 
dry,  823 
mains,  827 
pipe,  capacity,  308 

Reverse  cycle  of  refrigeration,  495,  749 
Reversed  return  system,  332 
Reynolds  number,  184 
Ringelmann  chart,  816 
Rock  wool  insulation,  100,  729 
Roof,  roofs,  f  ««, 

coefficients  of  transmission  of,  114 

conductivities  of,  101 

solar  radiation  on,  152,  153, 154 

ventilator,  672,  827 

Room  absorption  correction  charts,  557 
Room  control,  687 


S 

Salts  in  cooling  water,  509 
Saturated  air,  827 
Saturation,  fiber  point,  651 
Scale, 

in  boilers,  260 

Centigrade,  809 

on  equipment,  509 

Fahrenheit,  809 

in  pipe,  374 

Reaumur,  809 
School,  schools, 

air  flow  necessary  in,  70 

optimum  air  conditions,  65 

stokers  suitable  for,  201 

temperature  of,  in  winter,  134 

ventilation  in,  70 
Scrubbers,  499,  528 


Self-contained  control  system,  686 
Sensible  heat,  147,  827 
of  air,  12 
loss,  73 
of  water,  31 

Series  wound  motor,  703 
Service  connections,  770 
Sheet  metal,  for  ducts,  580,  641 
Shingles  air  leakage  through,  123 
Shunt  wound  motor,  703 
Skin  diseases,  607 
Silica  gel 

with  oxygen  chambers,  606 
regain  of  moisture  of,  626 
silicon  dioxide,  41 

equilibrium  conditions,  43 
system  of  adsorption,  39,  41,  491 
Single  phase  motor,  706 
Sizes  of  pipe,  (see  Pipe  Sizes) 
Skylights,  117,  671 
Sling  psychrometer,  814 
Slip-ring  wound  motors,  710 
Smoke,  79,  827 
abatement  of,  84 
measurement  of,  816 
recorders,  816 
tobacco,  70 
Smokeless  arch,  828 
Solar  heat,  151 
absorption  coefficients,  155 
effect  of, 
awnings,  155 
latitude,  152 
intensity  chart,  150 
occlusion  of,  84 
radiation, 
factors,  154 
through  glass,  152 
through  walls.  152 
time  lag,  155 
Solenoid  valves,  685 
Sound,  583,  (see  also  Noise) 
absorption  coefficients,  589 
control,  583 
duct  lining  factor,  593 
effect  on  duct  design,  567 
insulation  of,  589 
intensity,  335 
measurement  of,  584 
in  steam  heating  systems,  303 
unit  of,  583 
Specific  density,  3 
Specific  gravity,  2,  828 

of  fuel  gas,  176 
Specific  heat,  3,  828 
of  air,  5 

mean,  of  water  vapor,  3 
of  water,  31 
•  Specific  humidity,  8 
Specific  volume,  3,  828 

of  saturated  steam,  31 
Split  phase  motor,  707 
Split  system,  828 
air  conditioning  equipment,  461 

automatic  control  of,  689 
central  fan,  409 
unit  ventilators,  445 

Pbooths  for  painting,  640 


wiuls.  513 

efficiency  of,  512 
towers,  514 
distribution  of,  504 
generation  of,  504 
humidifiers,  505 

type  of  central  station  system,  423 
water  coolers,  482,  512 
Square  foot  of  heating  surface,  828 
Squirrel  cage  motors,  707 
Stack,  stacks,  378,  689 
effect,  670 

*  675 


wall,  380 
Stairways,  129 


HEATING   VENTHJITING  AIR  CONDITIONING   GUIDE  1938 


Standards, 
air,  82fe 

air  conditioning,  51 

A.S.H.V.E.  codes  and  standards,  248,  271,  839 
for  fuel  oil,  173 
for  pipe,  350 
for  radiators.  271 
for  welding,  368 
Static  pressure,  828 
Steam,  828 
coils,  452 

condensing  rates,  266 
consumption  for  buildings,  234 
flow,  Babcock's  formula,  502 
heat  content  of,  23 
heating  systems,  275,  828 

air-vent,  276,  270.  309,  310 

atmospheric,  283,  313,  321 

classification,  275 

condensation  return  pumps,  292 

connections,  (see  Connections,  Fittings) 

corrosion  of,  374 

design  of,  275,  301 

dirt  pockets,  328 

district  heating,  765 

dripping  of,  327 

electric,  745 

equivalent  length  of  run.  305 

gravity  systems,  275 

one-pipe,  275,  270,  309,  321 
two-pipe,  279,  310,  321 

with  high-pressure  steam,  313 

mechanical,  275 

orifice,  200,  303,  313,  321 

pipe,  301.  (set  also  Pip*) 


sizes,* 

pressure  drop  in.  278 

sub-atmospheric,  287,  293,  303,  313,  321 

types  of,  275 

vacuum,  285,  293,  295,  312,  830 

vapor,  303,  321,  830 
one-pipe,  280,  826 
two-pipe,  281,  282,  311,  829 

water  hammer  in,  303 

zone  control,  291 
high  pressure,  313 
jet  apparatus,  477 
meters  for,  774 
pressure,  313 
properties  of,  28 

requirements  of  buildings,  234,  777 
saturated,  properties  of,  31 
savings  in  use  of,  770 
superheated,  265, 828 

trap,  828 
tunnels,  769 
underground,  767 
in  unit  heaters,  440 
Sterilization  of  air,  600 
Stokers, 

apartment  house,  206 
automatic  control  of.  399,  699 
classes  of ,  204 
combustion  process,  209 

adjustments.  212 

efficiency,  212 
commercial,  206.  208 
controls,  213 
design  of,  201 
economy,  201 
household,  204 
mechanical,  201 
operating  requirements,  205 
overfeed  flat  grate,  201 
overfeed  inclined  grate,  202 
heating  boilers,  setting  heights,  211 
types  of,  201 

underfeed,  201,  829 

underfeed  rear  cleaning,  203 

underfeed  side  cleaning,  202 

of  hoi  water,  798,  SQ2 
temperatures  and  humidities  for,622 


Storm  sash,  125 

Streptococcus,  52 

Stroke,  heat,  599 

Sub-atmospheric  systems,  (see  also  Steam  Healing 

Systems) 
Suction, 

static  in  exhaust  systems,  635 
Summer, 

care  of  heating  boilers,  261 

comfort  zone,  64,  66 

conditioning,  apparatus  for,  423,  451,  499 

desirable  indoor  conditions  in,  66 

wind  velocities  and  directions,  148 
Sun, 

effect  on  heating  requirements,  291 

factor  of  cooling  load,  151 
Supply  outlets, 

selection  of,  381 

types  of,  389 
Surface, 

conductance,  828 

cooling,  431 
equipment,  431 
air  conditioning,  423 
ratings,  429 

extended,  gravity-indirect  heating  systems,  272 

heating,  829 
square  foot  of,  828 

radiant  heating,  759 
Sweating  of  pipe,  734 
Swimming  pool,  804 
Symbols, 

for  drawings,  836 

for  heat  transmission  formulae,  90 
Synchronous  motor,  711 
Synthetic  air  chart,  829 
Systems  of  control,  686 


Tank,  tanks, 

for  domestic  water  supply,  798,  802 

expansion,  349 

flush,  790 

Tees,  dimensions  of,  367 
Temperature, 

absolute.  819 

of  air  leaving  outlets,  428,  549 

apparatus  sensitive  to,  684,  819 

atmospheric,  184 

of  barns,  697 

base,  for  degree-day,  231,  234,  235 

basic,  3 

body,  53,  54.  754 

changes,  effect  on  human  beings,  55 

of  chimney  gases  184 

in  cities,  138, 148,  232 

of  city  water  main,  maximum,  508 

control  of,  213,  220,  225,  684,  750 
railway  air  conditioning,  613 

of  cooling  water,  482 

dew-point,  3,  822 

difference, 

between  floor  and  ceiling,  136,  226,  439 
desired,  determination  of,  674 
in  stacks  and  leaders.  378.  673 

dry-bulb,  2,  68,  823 
maximum  design,  148 
specified  in  winter,  134 

for  drying,  652 

effect  on  moisture  regain,  622 

effective,  58,  68,  135,  147,  823 
chart,  58,  60,  61,  62,  64 
for  maximum  comfort,  64,  756 

optimum,  62 

scale,  59 


of  gas  flame,  176 
in  industrial  ] 


I  processing,  722,  723 

inside,  63.  64,  134,  412 

surfaces,  758 
low,  insulation  for,  723 
of  mean  ulterior  surface,  758 


ALPHABETICAL  INDEX  TO  TECHNICAL  DATA  SECTION 


Temperature  (continued) 

mean  radiant,  754,  758 

measurement  of,  679,  683,  809 

in  occupied  space,  68 

outside,  136,  148 

radiation-convection,  762 

range  of  cooling  equipment,  511 

records  of  cities,  138,  148 

at  registers,  428,  649 

room,  10,  231,  820 

sensations,  57 

surface, 
of  man,  755 
mean  interior,  758 

systems  for  control  of,  213,  220,  225,  684,  750 

thermo-equivalent  conditions,  59 

•water  main,  maximum,  508 

of  well  water,  506 

wet-bulb,  11,  814,  830 
average,  511 
design,  147,  511 
as  index  of  air  distribution,  72 
maximum,  511 
Terminology,  819 
Test  codes,  248 
Test  instruments,  807 
Test  methods,  807 
Textile,  textiles, 

fibers,  regain  of  moisture,  621 

temperatures  and  humidities  for  processing,  623 
Theaters,  temperatures  of,  67, 134 
Therm,  829 

Thermal  resistance,  829 
Thermal  resistivity,  829 
Thermocouples,  807 
Thermodynamics,  829 

of  air  conditioning,  1 

laws  of,  826 

Thermo-equivalent  conditions,  59 
Thermometer,  809,  810,  811 
Thermocouple,  809 
Thermopile,  810 
Thermostat,  thermostats,  684,  829 

differential,  10,  683 

with  gas-fired  furnaces,  225 

immersion,  684 

insersion,  684 

location  of,  399 

with  oil  burners,  220 

pilot,  690 

with  radiant  heaters,  750 

room,  684 

surface,  684 

types  of,  673,  684 
Time  lag,  155 
Tobacco  smoke,  70 
Ton  of  refrigeration,  475,  829 
Ton-day  of  refrigeration,  829 
Total  heat,  829 
Total  pressure,  829 
Towers,  cooling,  482,  512,  514,  515 

return,  automatic,  298,  299 

with  steam  heating  systems,  281,  295 

types  of,  295 
Tube, 

Bourdon,  808 

Pitot,  811 

shell  and  tube  heat  exchanger,  483 
Tuberculosis,  83,  608 
Tubing,  copper  or  brass,  365 
Tunnels,  for  steam  pipe,  769 
Turbines,  with  unit  heaters,  444 
Two-pipe  steam  heating  systems,  (see  also  Steam 

Heating  Systems) 
Two  position  controls,  686 
Typhosus,  52 


Ultra-violet  light,  75, 84 
Underfeed  distribution  system,  829 
Underfeed  stoker,  229 
Underground  piping,  767 


Underwriters'  loop,  276, 318 

Unit  air  conditioners,  435, 451, 829 

air  distribution,  455 

classification,  436 

controls  for,  466 

cooling,  453 

dehumidification,  453 

filtering,  454 

heating,  452 

humidifying,  452 

location  of,  455 

residential,  460 

types  of,  436,  456 
Unit  coolers,  435,  449 

control  of,  695 

design  of,  450 

frost  removal  from,  450 
Unit  equipment,  435 

advantages,  435 

controls,  694 

miscellaneous,  464 
Unit  heaters,  435,  744,  829 

air  temperatures,  439 

control  of,  695 

direction  of  discharge,  441 

piping  connections,  442 

ratings  of,  441 
Unit  ventilators,  435,  444,  445,  446,  447,  829 

control  of,  696,  830 
Unwin  pressure  drop  formula,  766 
Up-feed  piping  systems,  275,  830,  (see  also  Steam 

Heating  Systems) 


Vacuum  gage,  808 
Vacuum  pumps,  292 
Vacuum  refrigeration,  477 

control  of,  701 
Vacuum  system  of  steam  heating,  (see  also  Steam 

Heating  Systems) 
Valve,  valves,  370 

apparatus  which  operates,  683 

on  boilers,  258,  316 

connections  for,  770 

control,  685 
with  steam  heating  systems,  315,  370 

with  high  pressure  steam,  313 

pressure-reducing,  314,  770 
ratings  of,  313 

for  radiators,  277,  581 

relief,  350 

roughing-in  dimensions,  373 

solenoid,  685 

sub-atmospheric  system,  587 

on  traps,  596 

types  of,  370 

for  water  supply,  788 
Velocity,  830 

81  m  ducts  of  buildings,  401,  569,  579 

in  exhaust  systems,  635,  642 
through  heating  units,  411 

measurement  of,  811 
*i  openings,  698 
sU  towers,  515 

sound  effect  of,  579 
chimney  gas,  187 

draft  loss,  192 
contours,  637 

in  ducts,  401,  635,  642,  811 
of  fans,  539 
head,  of  fluids,  563 
meter,  813 
steam, 

through  an  orifice.  313 

in  underground  pipes.  765 
water,  in  pipes,  336,  338,  339 
wind, 

choosing,  126 

measurement  of,  678 

on  natural  draft  equipment,  515 

in  natural  ventilation,  669 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 


\Vnt,  vents, 
on  traps,  2$C 
in  unit  ventilators,  446 

Ventilation,   51,   609,   830,    (see  also   Air   Dis- 
tribution) 
of  barns,  679 
in  drying,  Ml 
of  Ranges,  680 
in  hospitals,  598,  902 
mechanical,  77 

with  roof  ventilators,  672 
natural,  77 

air  changes  per  hour,  127 

control  of,  073 

general  rules  for,  677 

heat  to  be  removed  by.  675 
openings, 

doors,  *57I 

formula  to  determine  size  of,  009 

location  of,  675 

skylights,  671 

types  of,  670 

windows,  671 

for  public  buildings,  70,  575 
purpose  of,  675 

quantity  of  air  necessary  for,  70 
railway  air  conditioning,  609 
by  registers,  673 
for  schools,  70 
by  stacks,  670,  673 
symbols,  836 
Ventilator,  ventilators, 
resistance  of,  672 
roof.  672,  827 

unit,  235,  (see  also  Unit  Ventilators} 
Venturi  chimney,  180 
Vibration  of  machine  mountings,  587 
Vitiation  of  air,  51 
Volume, 

of  air  and  saturated  vapor,  12 
conversion  equations,  834 
furnace,  824 
specific,  3 

of  saturated  steam,  28 
of  water,  27 


W-Z 

Wall,  walls. 

absorption  of  heat.  155 

ah-  leakage  through,  122 

of  chimneys,  195 

condensation  onr  141 

fire,  640 

heat  transmission  coefficients  for,  89.  90,  97,  104, 
106, 108 

radiators,  output,  264 

solar  radiation  on,  152, 153 

time  lag  through,  155 
Warm  air  heating  systems,  830 

gas-fired  furnaces  for,  222 

gravity,  377 

mechanical,  393 

Washers,  air,  396,  49ft,  524,  525,  820 
Water, 

boiling  point  of,  27 

circulating,  temperature  of,  512.  724 

from  city  main*,  482,  508 

cooling, 

eojoipment,  507 
quantity.  509 
temperature,  606,  508 

composition  of ,  27 

demand,  785,  804 

density  of,  27 

domestic  supply,  783,  797 

evaporation  of.  516 

factor  of  usage,  785,  804 

flow  from  fixtures,  784,  785 

freezing,  733 

friction  losses  through  pipes,  791 

hammer,  303 

heaters,  411,  799 

heating,  783 


Water  (continued) 
hot, 

domestic  supply,  783,  797 
boilers,  799 
demand  for,  803 
electric  heating  of,  747 
pipe  sizes  for,  798 
storage  of,  798,  802 

heating  systems,  331,  (see  also  Hot  Water  Heat- 
ing Systems') 
indies  of  water,  825 
line, 

in  boilers,  258,  259,  275 
in  water  supply  systems,  790 
make-up,  516 
meters,  disc,  789 
pans,  for  humidification,  403 
pipe,  787 
pressures,  27 
probable  usage,  785,  804 
properties  of,  27 
as  a  refrigerant,  37,  45 
replacement  of,  516 
supply  piping,  783 
down-feed  systems,  786 
mains,  790 
up-feed  systems,  788 
temperature,  maximum  main,  508 

from  wells,  506 
thermal  properties  of,  27 
vapor,  5,  10,  12 

given  off  in  combustion  of  gas,  175 
heat  content,  12,  23 
mean  specific  heat  of,  3 
weight  of  saturated,  12 
Weatherstripping,  126 
Weight, 
of  air,  6 

conversion  equations,  834 
of  steam,  28 
of  vapor,  12 
of  water,  27 
Welding,  355,  366 

neck  flanges,  371,  372 
Well  water  refrigeration  control  of,  702 
Well  water  temperature,  506 
WeUbulb  temperature,  (see  Temperature,  Wet-bulb) 
Wet  return,  830 
Wind, 

in  cities,  138,  148 

effect  on  heating  requirements,  137 
forces  in  natural  ventilation,  121,  669,  675 
prevailing,  direction  of,  127,  148 
records  of  velocity  and  direction,  138,  148 
velocity  on  natural  draft  equipment,  515 
average,  127, 137,  148,  669 
equivalent,  hi  tall  buildings,  128 
used  in  calculations,  127 
Window,  windows,  671,  673 
air  leakage  through,  124, 126 
clearance  of  sash,  125 
coefficients  of  transmission  of,  117 
comparison  of  various  shades  for,  156 
crack,  124 

measurement  of,  124 
solar  radiation  through,  152 
storm  sash,  125 
Winter, 

comfort  zone,  63,  64 
conditioning,  apparatus  for,  393,  409 
cooling  in,  147 
humidification  in,  63,  68,  403 
inside  temperature,  134 
relative  humidity  in,  68 
temperatures,  138 
wind  velocities  and  directions,  138 
Zero,  absolute,  819 
Zone,  zoning, 

"for  air  conditioning  systems,  428 
automatic  control,  688 
comfort,  63,  64,  66,  821 
control  of  steam  heating  systems,  291 
for  large  heating  systems,  351 
neutral,  826 
water  supply  systems,  783 


HEATING  VENTILATING 
AIR  CONDITIONING 


Vol.  16      •  v          1938 

Chapter  1 

AIR,  WATER  AND  STEAM 

Dalton's  Law,  Temperatures,  Air  Properties,  Humidity,  Rela- 
tive Humidity,  Specific  Humidity,  Relation  of  Dew  Point  to 
Relative  Humidity,  Adiabatic  Saturation  of  Air,  Total  Heat 
and  Heat  Content,  Enthalpy,  Psychrometric  Chart,  Properties 
o£  Water,  Properties  of  Steam,  Rate  of  Evaporation 

A  IR  conditioning  has  for  its  objective  the  supplying  and  maintaining, 
,/JL  in  a  room  or  other  enclosure,  of  an  atmosphere  having  a  composition, 
temperature,  humidity,  and  motion  which  will  produce  desired  effects 
ugon  the  occupants  of  the  room  or  upon  materials  stored  or  handled  in  it. 

Dry  air  is  a  mechanical  mixture  of  gases  composed,  in  percentage  of 
volume,  as  follows1:  nitrogen  78.03,  oxygen  20.99,  argon  0.94,  carbon 
dioxide  0.03,  and  small  amounts  of  hydrogen  and  other  gases. 
- j ^Atmospheric  air  at  sea  level  is  given  in  percentage  by  volume  as:  N2 
77.08,  O2  20.75,  water  vapor  1.2,  A  0.93,  C02  0.03  and  H?  0.01.  The 
amount  of  water  vapor  varies  greatly  under  different  conditions  and  is 
frequently  one  of  the  most  important  constituents  since  it  affects  bodily 
comfort  and  greatly  affects  all  kinds  of  hygroscopic  materials. 

DALTON'S  LAW 

A  mixture  of  dry  gases  and  water  vapor,  such  as  atmospheric  air,  obeys 
Dalton's  Law  of  Partial  Pressures;  each  gas  or  vapor  in  a  mixture,  at  a 
given  temperature,  contributes  to  the  observed  pressure  the  same  amount 
that  it  would  have  exerted  by  itself  at  the  same  temperature  had  no  other 
gas  or  vapor  been  present.  If  p  =  the  observed  pressure  of  the  mixture 

international  Critical  Tables. 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 

and  pi,  fa,  pt,  etc.  =  the  pressure  of  the  gases  or  vapors  corresponding  to 
the  observed  temperature,  then 

P-#i  +  fc  +  />a,  etc.  (1) 

TEMPERATURES 

Air  is  said  to  be  saturated  at  a  given  temperature  when  the  water  vapor 
mixed  with  the  air  is  in  the  dry  saturated  condition  or,  what  is  the  equiva- 
lent, when  the  space  occupied  by  the  mixture  holds  the  maximum  pos- 
sible weight  of  water  vapor  at  that  temperature.  If  the  water  vapor 
mixed  with  the  dry  air  is  superheated,  i.e.,  if  its  temperature  is  above  the 
temperature  of  saturation  for  the  actual  water  vapor  partial  pressure,  the 
air  is  not  saturated. 

The  starting  point  of  most  applications  of  thermodynamic  principles  to 
air  conditioning  problems  is  the  experimental  determination  of  the  dry- 
bulb  and  wet-bulb  temperatures,  and  sometimes  the  barometric  pressure. 

The  dry-bulb  temperature  of  the  air  is  the  temperature  indicated  by  any 
type  of  thermometer  not  affected  by  the  water  vapor  content  or  relative 
humidity  of  the  air.  The  wet-bulb  temperature  is  determined  by  a  thermo- 
meter with  its  bulb  encased  in  a  fine  mesh  fabric  bag  moistened  with  clean 
water  and  whirled  through  the  air  until  the  thermometer  assumes  a 
steady  temperature.  This  steady  temperature  is  the  result  of  a  dynamic 
equilibrium  between  the  rate  at  which  heat  is  transferred  from  the  air  to 
the  water  on  the  bulb  and  the  rate  at  which  this  heat  is  utilized  in  evapora- 
ting moisture  from  the  bulb.  The  rate  at  which  heat  is  transferred  from 
the  air  to  the  water  is  substantially  proportional  to  the  wet-bulb  depres- 
sion (t  —  /l),  while  the  rate  of  heat  utilization  in  evaporation  is  propor- 
tional to  the  difference  between  the  saturation  pressure  of  the  water  at 
the  wet-bulb  temperature  and  the  actual  partial  pressure  of  the  water 
vapor  in  the  air  (e}  —  e).  Carrier's  equation  for  this  dynamic  equilibrium 
is 

1-c  B  -j 

t  -  /'        2800  -  1.3*' 

In  the  form  commonly  used, 


where 

e  —  actual  partial  pressure  of  water  vapor  in  the  air,  inches  of  mercury. 
c1  =  saturation  pressure  at  wet-bulb  temperature,  inches  of  mercury. 
B  =  barometric  pressure,  inches  of  mercury. 

/  =  dry-bulb  temperature,  degrees  Fahrenheit. 
t*  =  wet-bulb  temperature,  degrees  Fahrenheit. 

Formula  2b  may  be  used  to  determine  the  actual  partial  pressure  of  the 
water  vapor  in  a  dry  air-water  vapor  mixture.  Then,  from  Dalton's  Law 
of  Partial  Pressures,  Equation  1,  it  follows  that  the  partial  pressure  of  the 
dry  air  is  (B  -  e). 

If  a  mixture  of  dry  air  and  water  vapor,  initially  unsaturated,  be  cooled 


CHAPTER  1.   AIR,  WATER  AND  STEAM 


at  constant  pressure,  the  temperature  at  which  condensation  of  the  water 
vapor  begins  is  called  the  dew-point  temperature.  Clearly  the  dew-point 
is  the  saturation  temperature  corresponding  to  the  actual  partial  pressure, 
e,  of  the  water  vapor  in  the  mixture. 

AIR  PROPERTIES 

Density  is  variously  defined  as  the  mass  per  unit  of  volume,  the  weight 
per  unit  of  volume,  or  the  ratio  of  the  mass,  or  weight,  of  a  given  volume 
of  a  substance  to  the  mass,  or  weight,  of  an  equal  volume  of  some  other 
substance  such  as  water  or  air  under  standard  conditions  of  temperature 
and  pressure.  The  term  specific  gravity  is  more  commonly  used  to  express 
the  latter  relation  but,  when  the  gram  is  taken  as  the  unit  of  mass  and  the 
cubic  centimeter  as  the  unit  of  volume,  density  and  specific  gravity  have 
the  same  meaning.  The  term  specific  density  is  sometimes  used  to  dis- 
tinguish the  weight  in  pounds  per  cubic  foot;  and  as  here  used,  density  is 
the  weight  in  pounds  of  one  cubic  foot  of  a  substance. 

The  density  of  air  decreases  with  increase  in  temperature  when  under 
constant  pressure.  The  density  of  dry  air  at  70  F  and  under  standard 
atmospheric  pressure  (29.921  in.  of  Hg)  is  approximately  0.075  Ib  (see 
Table  1),  while  that  of  a  mixture  of  air  and  saturated  water  vapor  at  the 
same  temperature  and  barometric  pressure  is  only  about  0.0742  Ib.  In 
the  mixture  the  density  of  the  dry  air  is  0.07307  and  that  of  the  vapor  is 
0.00115  Ib  (see  Table  2). 

In  order  to  make  comparisons  of  air  volumes  or  velocities  it  is  necessary 
to  reduce  the  observations  to  a  common  pressure  and  temperature  basis. 
The  basic  pressure  is  usually  taken  as  29.921  in.  of  Hg,  but  no  basic  tem- 
perature is  universally  recognized.  Common  temperatures  for  this 
purpose  are  32  F,  60  F,  68  F,  and  70  F.  Since  70  F  is  the  most  commonly 
specified  temperature  to  which  rooms  for  human  occupancy  must  be 
heated,  it  is  usually  understood,  when  no  other  temperature  is  specified, 
that  70  F  is  the  basic  temperature  for  measuring  the  volume  or  the 
velocity  of  air  in  heating  and  ventilating  work. 

The  specific  volume  of  air  is  the  volume  in  cubic  feet  occupied  by  one 
pound  of  the  air.  Under  constant  pressure  the  specific  volume  varies 
inversely  as  the  density  and  directly  as  the  absolute  temperature. 

The  specific  heat  of  air  is  the  number  of  Btu  required  to  raise  the  tem- 
perature of  1  Ib  of  air  1  F.  Distinction  should  always  be  made  between 
the  instantaneous  specific  heat  at  any  existent  temperature  and  the  mean 
specific  heat,  which  is  the  average  specific  heat  through  a  given  tempera- 
ture range.  The  mean  specific  heat  is  the  value  required  in  most  calcu- 
lations. The  specific  heats  at  constant  pressure,  Cp,  and  the  specific 
heats,  Cv,  at  constant  volume  are  different.  The  specific  heat  at  constant 
pressure  is  commonly  used  and  it  varies,  under  a  pressure  of  one  atmos- 
phere, from  a  minimum  at  32  F  from  which  it  increases  with  either  increase 
or  decrease  of  temperature.  The  value  of  0.24,  as  the  mean  specific  heat 
at  constant  pressure,  is  sufficiently  accurate  for  use  at  ordinary  tem- 
peratures. Values  for  instantaneous  and  mean  specific  heats  are  given 
in  Table  3. 

The  mean  specific  heat  of  'water  vapor  at  cqnstant  pressure  is  taken  as 
0.45  for  all  general  engineering  computations. 


HEATING   VENTILATING  AIR  CONDITIONING  GUIDE  1938 


TABLE  1.    PROPERTIES  OF  DRY  AiRa 

Barometric  Pressure  29.921  In.  of  Hg 


TaMWRATTRE            WEIGHT  POUNDS 
DIG  F                    PBB  Cc  FT 

i 

RATIO  OF 
VOLUME  TO 
VOLTME  AT  70  F 

BTTJ  ABSORBED  BY 
ONE  CTT  FT  DRY 
Am  PEE  DEQ  F 

Cu  FT  DRY 
AIR  WARMED 
ONE  DEG 
PER  BTTJ 

0 

0.08633 

0.8678 

0.02077 

48.15 

10 

0.08449 

0.8867 

0.02030 

49.26 

20 

0.08273 

0.9056 

0.01986 

50.35 

30                   0.08104 

0.9245 

0.01944 

51.44 

40 

0.07942 

0.9433 

0.01905 

52.49 

50 

0.07785 

0.9624 

0.01868 

53.36 

60 

0.07636 

0.9811 

0.01832 

54.44 

70 

0.07492 

1.0000 

0.01798 

55.62 

80 

0,07353 

1.0189 

0.01765 

56.66 

90 

0.07219 

1.0378 

0.01733 

57.70 

100 

0.07090 

1.0567 

0.01702 

58.75 

110 

0.06966 

1.0755 

0.01672 

59.81 

120 

0.06845 

1.0946 

0.01643 

60.86 

130 

0.06729 

1.1133 

0.01616 

61.88 

140 

0.06617 

1.1322 

0.01589 

62.93 

150 

0.06509 

1.1510 

0.01563 

63.98 

160 

0.06403 

1.1701 

0.01538 

65.02 

180 

0.06203 

1.2078 

0.01490 

67.11 

200 

0.06015 

1.2456 

0.01446 

69.24 

220 

0.05838 

1.2832 

0.01403 

71.27 

240 

0.05671 

1.3211 

0.01364 

73.31 

260 

0.05514 

1.3587 

0.01326 

75.41 

280 

0.05365 

1.3965 

0.01291 

77.46 

300 

0.05223 

1.4344 

0.01257 

79.55 

350 

0.04901 

1.5287 

0.01181 

84.67 

400 

0.04615 

1.6234 

0.01114 

89.67 

450 

0.04362 

1.7176 

0.01054 

94.87 

500 

0.04135 

1.8119 

0.01001 

99.01 

550 

0.03930 

1.9064 

0.00953 

104.93 

600 

0.03744 

2.0011 

0.00908 

110.13 

700 

0.03422 

2.1893 

0.00833 

120.05 

800 

0.03150 

2.3784 

0.00769 

130.04 

900 

0.02911 

2.5737 

0.00713 

140.25 

1000 

0.02718 

2.7564 

0.00668 

149.70 

H>  Sev5M-  b38ed  on  the  instantaneous  specific  heats  of  air. 


CHAPTER  1.   AIR,  WATER  AND  STEAM 


TABLE  2.    PROPERTIES  OF  SATURATED  AiRa 

Weights  of  Air,  Vapor  and  Saturated  Mixture  of  Air  and  Vapor  at  29.921  In.  of  Hg 


TEMP. 
DsoF 

WEIGHT  IN  A  CUBIC  FOOT  OP  MEKTUBE 

BTU 
ABSORBED 
BY  ONE 
CUBIC 
FOOT 
SAT.  Am 
PER  DEO  F 

CUBIC 
FEET 
SAT.  Am 
WARMED 
ONE  DEO 
PEE  BTU 

SPECIFIC 
HEAT  BTU 
PER  POUND 

OP 

MIXTURE 

Weight  of 
Dry  Air 
Pounds 

Weight  of 
Vapor 
Pounds 

Total  Weight 
ofMirture 
Pounds 

0 

0.08622 

0.000068 

0.08629 

0.02078 

48.12 

0.2408 

10 

0.08431 

0.000111 

0.08442 

0.02031 

49.24 

0.2406 

20 

0.08244 

0.000177 

0.08262 

0.01987 

50.33 

0.2405 

30 

0.08060 

0.000278 

0.08088 

0.01946 

51.39 

0.2406 

40 

0.07876 

0.000409 

0.07917 

0.01908 

52.41 

0.2410 

50 

0.07692 

0.000587 

0.07751 

0.01872 

53.42 

0.2415 

60 

0.07503 

0.000828 

0.07586 

0.01838 

54.41 

0.2423 

70 

0.07307 

0.001151 

0.07422 

0.01805 

55.40 

0.2432 

80 

0.07099 

0.001578 

0.07257 

0.01775 

56.34 

0.2446 

90 

0.06877 

0.002134 

0.07090 

0.01747 

57.24 

0.2464 

100 

0.06634 

0.002851 

0.06919 

0.01721 

58.11 

0.2487 

110 

0.06361 

0.003762 

0.06737 

0.01696 

58.96 

0.2517 

120 

0,06057 

0.004912 

0.06548 

0.01675 

59.70 

0.2558 

130 

0.05712 

0.006344 

0.06346 

0.01657 

60.35 

0.2611 

140 

0.05317 

0.008116 

0.06129 

0.01642 

60.91 

0.2679 

150 

0.04863 

0.010284 

0.05891 

0.01630 

61.35 

0.2767 

160 

0.04339 

0.012919 

0.05631 

0.01624 

61.58 

0.2884 

170 

0.03733 

0.016092 

0.05342 

0.01621 

61.69 

0.3034 

180 

0.03033 

0.019888 

0.05022 

0.01624 

61.58 

0.3234 

190 

0.02228 

0.024384 

0.04666 

0.01633 

61.24 

0.3500 

200 

0.01298 

0.029700 

0.04268 

0.01649 

60.64 

0.3864 

210 

0.00230 

0.035932 

0.03616 

0.01672 

59.81 

0.4624 

212 

0.00000 

0.037286 

0.03729 

0.01818 

55.01 

0.4875 

^Compiled  by  W.  H.  Severns,  based  on  the  instantaneous  specific  heats  of  air. 

TABLE  3.    SPECIFIC  HEATS  OF  DRY  AiRa 

Constant  Barometric  Pressure  of  29.921  In.  of  Hg 


TEMPERATURE 
DE0F 

INSTANTANEOUS 

OSTBUB 

SPECIFIC  HEAT 

TEMPERATUBE 
RANGE 
DBGF 

MEAN 
SPECIFIC 
HEAT 

-301.0 

0.2520 

32  to  212 

0.2401 

-108.4 

0.2430 

32  to  392 

0.2411 

32.0 

0.2399 

32  to  752 

0.2420 

212.0 

0.2403 

32  to  1112 

0.2430 

392.0 

0.2413 



752.0 

0.2430 





1112.0 

0.2470 





•Compiled  by  W.  H.  Severna,  based  on  data  given  in  the  International  Critical  Tables. 

5 


HEATING  VENTILATING  AIR  CONDITIONING   GUIDE  1938 


',  -*  ^  ^       ,H  fs,  r*       ,>,  r 


-^ 


000       000       000       OOP 
rf« -*1  «"O       f*5  ?O  c-1       cs  •»— i  *H       *— i  »-H  O 


o 

H 

S 


a 

2 


I 


I 


o  | 

g    0 

1* 

Is 


«sa: 


jo*  do     odd     dod     ddo*     odd     o'o'd     POP 
f o*  cc  oo" "  "r-^r^o      o~o~o    ~r;;ro6~ci'      O~CN"^      o  oTco \o  oo  •»- 


!  j?  5,  J2      jddd     odd     odd     odd     OOP"     P'P'O     PPP 


~O~  CM'  "" 


es 


!ooq  qoq  qqq  S8q  qqq  qqS 

I  o*  o*  d  ooo  odd  odd  odd  odd  PPP 

>C  CC  CN     CM  T-l  TH     T-H  TH  O 


OOO   OOO   OO'O   000   000   OOO"   OOO 


I  ooo  coo  OPO  odd  ooo"  odd  POP 


§ 


o 


ooo  o      o"  d  d  o*  o*  odd  odd  odd 


ooo  ooo  ooo  odd  odd  odd  odd 


IMS* 


odd  do'd 

"O~vCTvO   NO  10  10 


8±$ 

«! 

gfci 


6 


uiG 


§§3    _ 

ooo  odd  odd  odd  odd.  odd  odd 


Ri 


h  w      co  co  CM 


4  CN "*H         r-1  TH  p 

3£J£3      cs 


odd  odd  odd  odd  ddo 


ooo  ddo* 


IO  to  >O        vOvOt*-        00  O\  *H 

d  o*  d     PPP     ddd 


oopvo  **»  co  cs 

OOCN»0  0\^S 

t^vO-^  <N  TH  O\ 

f**t*>t>-  r*-t^\o 

qqq  qqq 

odd  odd 


)  UO  00          T-I  V 


ooo     PPP 


PT)  CS  CN        OO  OO  O        CM  CS  CO 

odd     PPP*     ddd 


BSS 


SSS    SSS 

PPP       PPP 


3iO  »O 


H  CO    COCOCM    CM  CS  TH    »H  ^H  C 


ooo  ooo  ooo  ooo  ood 


odd  o'o'd 


PPP  ooo  POP  ppp  PPP  odd  odd 


88  III 

^ss  sss 

ooo     odd 


sis  sss  ssi 

odd     odd     ddo" 


S.2.3.  S8S 

POP  odd 


oo< 


o    005 


5 
11 

s  5 


•85 


J5 

II 
IJ 


i 

1 5* 

I 


Hi 


CHAPTER  1.   AIR,  WATER  AND  STEAM 


Table  4  is  intended  to  aid  in  determining  the  density  of  moist  air, 
taking  into  account  its  temperature,  pressure,  and  moisture  content. 

Example  1.  To  show  the  use  of  Table  4:  Given  air  at  83  F  dry-bulb  and  68  F  wet- 
bulb  (or  a  depression  of  15  deg)  with  a  barometric  pressure  of  29.40  in.  of  mercury. 
What  will  be  the  weight  of  this  air  in  pounds  per  cubic  foot? 

Solution.  From  Table  4  the  weight  of  saturated  air  at  80  F  and  29.00  in.  barometer  is 
found  to  be  0.07034  Ib  per  cubic  foot.  There  is  a  decrease  of  0.00015  Ib  per  degree  dry- 
bulb  temperature  above  80  F.  There  is  an  increase  of  0.00025  Ib  for  each  0.1  in.  above 
29.00  in.  From  the  last  column  of  Table  4  it  is  found  that  there  is  an  increase  of  approxi- 
mately 0.000035  Ib  per  degree  wet-bulb  depression  when  the  dry-bulb  is  83  F.  Tabu- 
lating the  items: 

0.07034  =  weight  of  saturated  air  at  80  F  and  29.00  bar. 

-  0.00045  «  decrement  for  3  deg  dry-bulb,  3  X  0.00015. 

+  0.00100  =  increment  for  0.4  in.  bar.,  4  X  0.00025. 

+  0.00053  =  increment  for  15  deg  wet-bulb  depression,  15  X  0.000035. 

0.07142  =  weight  in  pounds  per  cubic  foot  of  air  at  83  F  dry-bulb,  68  F  wet-bulb, 
29.40  in.  bar. 

It  is  usual  to  assume  that  dry  air,  moist  air,  and  the  water  vapor  in  the 
air  follow  the  laws  of  perfect  gases.  This  assumption  while  not  absolutely 
true,  especially  with  saturated  vapor  at  temperatures  much  above  140  F, 
is  sufficiently  accurate  for  practical  purposes  and  it  greatly  simplifies 
computations. 

Boyle's  Law  refers  to  the  relation  between  the  pressure  and  volume  of  a 
gas,  and  may  be  stated  as  follows :  With  temperature  constant,  the  volume  of 
a  given  weight  of  gas  varies  inversely  as  its  absolute  pressure.  Hence,  if 
PI  and  P2  represent  the  initial  and  final  absolute  pressures,  and  V\  and 
F2  represent  corresponding  volumes  of  the  same  mass,  say  one  pound  of 

•FT  -p 

gas,  then^~  =  -=2,  or  Pi  Vi  =  P2  F2,  but  since  Pi  7i  for  any  given  case  is 

V2      Jri 

a  definite  constant  quantity,  it  follows  that  the  product  of  the  absolute 
pressure  and  volume  of  a  gas  is  a  constant,  or  PV  =  C,  when  T  is  kept 
constant.  Any  change  in  the  pressure  and  volume  of  a  gas  at  constant 
temperature  is  called  an  isothermal  change. 

Charles1  Law  refers  to  the  relation  among  pressure,  volume,  and  tem- 
perature of  a  gas  and  may  be  stated  as  follows :  The  volume  of  a  given 
weight  of  gas  varies  directly  as  the  absolute  temperature  at  constant  pressure, 
and  the  pressure  varies  directly  as  the  absolute  temperature  at  constant 

volume.    Hence,  when  heat  is  added  at  constant  volume,  Fc,  the  resulting 
•p       *p 

equation  is  ^  =  -=r,  or,  for  the  same  temperature  range  at  constant  pres- 
"\      -LI 

Vz      T* 

sure,  PC,  the  relation  is  «  =  TF- 
1/1/1 

In  general,  for  any  weight  of  gas,  T7,  since  volume  is  proportional  to 
weight,  the  relation  among  P,  F,  and  T  is 

PV  =  WRT  (3) 

where 

P  «=  the  absolute  pressure  of  the  gas,  pounds  per  square  foot. 
V  =  the  volume  of  the  weight  W,  cubic  feet. 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

W  =  the  weight  of  the  gas,  pounds.  » 

R  *  a  constant  depending  on  the  nature  of  the  gas.    The  average  value  of  R  for  air 

is  53.34. 
T  «  the  absolute  temperature,  degrees  Fahrenheit. 

This  is  the  characteristic  equation  for  a  perfect  gas,  and  while  no  gases 
are  perfect  in  this  sense,  they  conform  so  nearly  that  Equation  3  will 
apply  to  most  engineering  computations. 

HUMIDITY 

Humidity  is  the  water  vapor  mixed  with  dry  air  in  the  atmosphere. 
Absolute  humidity  has  a  multiplicity  of  meanings,  but  usually  the  term 
refers  to  the  weight  of  water  vapor  per  unit  volume  of  space  occupied, 
expressed  in  grains  or  pounds  per  cubic  foot.  With  this  meaning,  absolute 
humidity  is  nothing  but  the  actual  density  of  the  water  vapor  in  the 
mixture  and  might  better  be  so  called.  A  study  of  Keenan's  Steam 
Tables2  indicates  that  water  vapor,  either  saturated  or  super-heated,^  at 
partial  pressures  lower  than  4  in.  of  mercury  may  be  treated  as  a  gas  with 
a  gas  constant  R  of  1.21  in  the  characteristic  equation  of  the  gas  pV  — 
wR  (t  +  460).  Within  such  limits,  the  density  (d)  of  water  vapor  is 


1.2!  (-f  460) 
5785  e 


(Pounds  ***  cubic  foot) 


460 


(grains  per  cubic  foot)  (4b) 


where 

e  —  actual  partial  pressure  of  vapor,  inches  of  mercury. 
t  —  dry-bulb  temperature,  degrees  Fahrenheit. 

Specific  Humidity 

It  simplifies  many  problems  which  deal  with  mixtures  of  dry  air  and 
water  vapor  to  express  the  weight  or  the  mass  of  the  vapor  in  terms  of  the 
weight  or  the  mass  of  dry  air.  If  the  weight  of  the  water  vapor  in  a 
mixture  be  divided  by  the  weight  of  the  dry  air,  and  the  weight  of  dry  air 
be  made  unity,  we  have  an  expression  of  the  weight  of  water  vapor  carried 
by  a  unit  weight  of  dry  air.  This  relation  has  no  generally  accepted  name. 
It  has  been  variously  called:  mixing  ratio,  proportionate  humidity,  mass 
or  density  ratio,  absolute  humidity,  and  specific  humidity.  Of  all  these 
terms  specific  humidity  is  the  most  suggestive  of  the  meaning  which  it  is 
desired  to  express  and  it  has  found  considerable  use  in  this  sense  even 
though  it  is  defined  in  International  Critical  Tables  as  the  ratio  of  the 
mass  of  vapor  to  the  total  mass.  It  will  be  understood  here  that  specific 
humidity  refers  to  the  weight  of  water  vapor  carried  by  one  pound  of 
dry  air. 

The  gas  constant  for  dry  air,  when  the  partial  pressure  of  the  air  is 
expressed  in  inches  of  Hg,  is  0.753;  so  that  the  specific  humidity,  if 
represented  by  W,  is 


"Published  by  American  Society  of  Mechanical  Engineers,  see  abstract  in  Table  8. 

8 


CHAPTER  1.   AIR,  WATER  AND  STEAM 


W  - 


B-e 


1.21  (t  +  460) 
=  0.622       - 


0.753  (t  +  460) 
(pounds) 


(5a) 
(5b) 


-4354  (£)  (grains) 

where 

e  =  actual  partial  pressure  of  vapor,  inches  of  mercury. 
B  =  total  pressure  of  mixture  (barometric  pressure),  inches  of  mercury. 

Relative  Humidity 

Relative  humidity  ($)  is  either  the  ratio  of  the  actual  partial  pressure, 
e,  of  the  water  vapor  in  the  air  to  the  saturation  pressure,  et,  at  the  dry- 
bulb  temperature,  or  the  ratio  of  the  actual  density,  d,  of  the  vapor  to 
the  density  of  saturated  vapor,  dt,  at  the  dry-bulb  temperature.  That  is: 

The  relative  humidity  of  a  given  mixture  at  a.giyen  temperature  is  not 
the  same  as  the  specific  humidity,  W,  of  the  mixture  divided  by  the 
specific  humidity,  Wt,  of  saturated  vapor  at  the  same  temperature,  for 
from  Equations  5a  and  6 


Wt  -  °-622 


0.622 


(-=*-) 

\  B-et  ) 


B  — 


(7) 


The  specific  humidity  of  an  unsaturated  air-vapor  mixture  cannot, 
therefore,  be  accurately  found  by  multiplying  the  specific  humidity  of 
saturated  vapor  by  its  relative  humidity;  although  the  error  is  usually 
small  especially  when  the  relative  humidity  is  high. 

With  a  relative  humidity  of  100  per  cent,  the  dry-bulb,  wet-bulb,  and 
dew-point  temperatures  are  equal.  With  a  relative  humidity  less  than 
100  per  cent,  the  dry-bulb  exceeds  the  wet-bulb,  and  the  wet-bulb  exceeds 
the  dew-point  temperature. 

RELATION  OF  DEW  POINT  TO  RELATIVE  HUMIDITY 

A  peculiar  relationship  exists  between  the  dew-point  and  the  relative 
humidity  and  this  is  found  most  useful  in  air  conditioning  work.  This 
relationship  is,  that  for  a  fixed  relative  humidity  there  is  substantially  a 
constant  difference  between  the  dew-point  and  the  dry-bulb  temperature 
over  a  considerable  temperature  range.  Table  5,  giving  the  dry-bulb  and 
dew-point  temperatures  and  the  dew-point  differentials  for  50  per  cent 
relative  humidity,  illustrates  this  relationship  clearly. 

TABLE  5.   TEMPERATURES  FOR  50  PER  CENT  RELATIVE  HUMIDITY 


Dry-bulb  temperature..—...  ..  

65.0 

70.0 

75.0 

80.0 

85.0 

90.0 

Dew-point  temperature.  

45.8 

50.5 

55.25 

59.75 

64.25 

68.75 

Difference  between  dew-point  and  dry- 
bulb  temperature  

19.2 

19.5 

19.75 

20.25 

20.75 

21.25 

HEATING  VENTILATING  AIR  CONDITIONING   GUIDE  1938 

It  will  be  seen  from  an  inspection  of  this  table  that  the  difference 
between  the  dew-point  temperature  and  the  room  temperature  is  approxi- 
mately 20  deg  throughout  this  range  of  dry-bulb  temperatures  or,  to 
be  more  exact,  the  differential  increases  only  10  per  cent  for  a  range  of 
practically  25  deg. 

This  principle  holds  true  for  other  humidities  and  is  due  to  the  fact 
that  the  pressure  of  the  water  vapor  practically  doubles  for  every  20  deg 
through  this  range. 

The  approximate  relative  humidity  for  any  difference  between  dew- 
point  and  dry-bulb  temperature  may  be  expressed  in  per  cent  as: 

100 
2^  W 

where 

/I  =  dew-point  temperature. 

This  principle  is  very  useful  in  determining  the  available  cooling  effect 
obtainable  with  saturated  air  when  a  desired  relative  humidity  is  to  be 
maintained  in  a  room,  even  though  there  may  be  a  wide  variation  in  room 
temperature.  This  problem  is  one  which  applies  to  certain  industrial  con- 
ditions, such  as  those  in  cotton  mills  and  tobacco  factories,  where  re- 
latively high  humidities  are  carried  and  where  one  of  the  principal  prob- 
lems is  to  remove  the  heat  generated  by  the  machinery.  It  also  permits 
the  use  of  a  differential  thermostat,  responsive  to  both  the  room  tempera- 
ture and  the  dew-point  temperature,  to  control  the  relative  humidity 
in  the  room. 

Table  6  gives,  for  different  temperatures,  the  density  of  saturated  vaporr— 
dt,  the  weight  of  saturated  vapor  mixed  with  1  lb  of  dry  air,  Wt,  (at  a 
relative  humidity  of  100  per  cent  and  a  barometric  pressure,  B,  of  29.92  in. 
of^mercury),  the  specific  volume  of  dry  air,  and  the  volume  of  an  air-vapor 
mixture  containing  1  Ib  of  dry  air  (at  a  relative  humidity  of  100  per  cent 
and  a  pressure  of  29.92  in.  of  mercury).  The  preceding  equations  or  the 
data  from  Table  6  may  be  conveniently  used  in  solving  the  following- 
typical  problems:  5 


*&  » to  be  maintained  at  70  F  with  a  relative 
=  04)  when  the  outside  air  is  at  0  F  and  70  per  cent 
a  baro<netric  Press^'  *>  of  29.92  in.  of  mercury     Fmd 
t0  *"*  V*™*  °f  dry  air  and  ***  dew'P°int  temperature 

Solution.    From  Equation  5a  and  Table  6, 

Wl  =  0.622  (29.92-0.0264)  "  °-000548  lb  P«r  Pound  of  dry  air. 

W,  -  0.622  (  29.92X-°  olfg  )  =  °'00618  lb  *>*  P°und  of  dry  air. 


An  approximation  of  the  same  result  from  Table  6  is 

Wk  -•  0.4  X  0.01574  =  0.006296  lb  per  pound  o?dry  ai? 

10 


CHAPTER  1.   AIR,  WATER  AND  STEAM 


The  water  vapor  added  per  pound  of  dry  air  is  approximately  0.00574636  Ib  and  the 
dew-point  temperature  is  approximately  45  F.  The  degree  of  approximation  is  evident. 

Example  8.  Dehumidifying  and  Cooling.  Air  with  a  dry-bulb  temperature  of  84  F, 
a  wet-bulb  of  70  F,  or  a  relative  humidity  of  50  per  cent  ($  =  0.5),  and  a  barometric 
pressure,  B,  of  29.92  in.  of  mercury  is  to  be  cooled  to  54  F,  Find  the  dew-point  tem- 
perature of  the  entering  air  and  the  weight  of  vapor  condensed  per  pound  of  dry  air. 

Solution.    From  Equation  5a  and  Table  6, 

wl  -  0.622          -  "  °'01248  lb  per  pound  of  dry  air* 


°'622     "  "  °-00887  Ib  Per  P°Und 


Since  W\  —  Wt  when  t  —  63.4  F,  this  is  the  dew-point  temperature  of  the  entering  air. 
The  weight  of  vapor  condensed  is  (Wi  —  W^  or  0.00361  lb  per  pound  of  dry  air. 

An  approximate  result  is 

Wi  -  0.5  X  0.02543  -  0.012715  lb  per  pound  of  dry  air. 

Wt  =  1  X  0.008856  =  0.008856  lb  per  pound  of  dry  air,  since  the  exit  air  is  saturated. 

Since  W\  —  Wt  at  t  —  64  F,  this  is  the  dew-point  temperature  of  the  entering  air. 
The  weight  of  vapor  condensed  is  0.003859  lb  per  pound  of  dry  air.  The  degree  of  approxi- 
mation is  again  evident. 

ADIABATIC  SATURATION  OF  AIR 

The  process  of  adiabatic  saturation  of  air  is  of  considerable  importance 
in  air  conditioning.  Suppose  that  1  lb  of  dry  air,  initially  unsaturated  but 
carrying  W  lb  of  water  vapor  with  a  dry-bulb  temperature,  /,  and  a  wet- 
bulb  temperature,  f,  be  made  to  pass  through  a  tunnel  containing  an 
exposed  water  surface.  Further  assume  the  tunnel  to  be  completely  in- 
sulated, thermally,  so  that  the  only  heat  transfer  possible  is  that  between 
the  air  and  water.  As  the  air  passes  over  the  water  surface,  it  will  gradu- 
ally pick  up  water  vapor  and  will  approach  saturation  at  the  initial  wet- 
bulb  temperature  of  the  air,  if  the  water  be  supplied  at  this  wet-bulb  tem- 
perature. During  the  process  of  adiabatic  saturation,  then,  the  dry-bulb 
temperature  of  the  air  drops  to  the  wet-bulb  temperature  as  a  limit,  the 
wet-bulb  temperature  remains  substantially  constant,  and  the  weight  of 
water  vapor  associated  with  each  pound  of  dry  air  increases  to  Wv,  as  a 
limit,  where  Wv  is  the  weight  of  saturated  vapor  per  pound  of  dry  air  for 
saturation  at  the  wet-bulb  temperature. 

Example  4-  If  air  with  a  dry-bulb  of  85  F  and  a  wet-bulb  of  70  F  be  saturated  adia- 
batically  by  spraying  with  recirculated  water,  what  will  be  the  final  temperature  and  the 
vapor  content  of  the  ah-? 

Solution.  The  final  temperature  will  be  equal  to  the  initial  wet-bulb  temperature  or 
70  F,  and  since  the  air  is  saturated  at  this  temperature,  from  Table  6,  W  -  0.01574  lb 
per  pound  of  dry  air. 

In  the  adiabatic  saturation  process,  since  the  heat  given  up  by  the  dry 
air  and  associated  vapor  in  cooling  to  the  wet-bulb  temperature  is  utilized 
in  evaporation  of  water  at  the  wet-bulb  temperature,  W»  H.  Carrier  has 
pointed  out8  that  the  equation  for  the  process  of  adiabatic  saturation,  and 
hence  for  a  process  of  constant  wet-bulb  temperature,  is: 


'Rational  Psychrometric  Formulae,  by  W.  H.  Carrier  (A.S.M.E.  Transactions,  Vol.  33,  1911,  p  1005.) 

11 


HEATING  VENTILATING  AIR  CONDITIONING  GUIDE  1938 


M 

8  ' 


I     IJN 


S  S3  IS  15  S 
oooo  ooooo  ooooo 

H  iH  iH  r-l  i-l        ,-<  ,-1  ,H  tH  T-l        ^  »H  »H  iH  iH 


<M      (N(N(NM(N 
!!!!         |    I     |    I     J         I    I    I     I     I          I     I     I     1     I         I     I     I     I     I          I     I     I     I     I          I     I     I     I    I 


OOi~l      CCOCOr-IC 


QiHCOCOOO      i-t 


0000060006    0606060606    0606060606    060600606    060000     0  000  os 


iHeeooOT-i    cooooi-ieo     COOOTHCOCD     OQIHCQCOOO    i-HcoeooiH     TPCDQIHTH     oosi-t^co 

OOCCCOW^      •^•^•^lOifl      »CiO«O«OeO      «Dt-t-t«-^      OOOOOOOOO       CSOSOOO      OO»HiHi-l 


00000     00000      00000      00000      00000      0 06 06 cJ oi    osoicooioj 


I 

I 


IIP  III 


Soooo    oooc 


eo«4iiONo>     ON- 


no    UDOCOO«O    r-no^Ho 

2S  2§5?S^§   g§2g 

is  sisls  ssii 


gsggg 
sssss 


I 

3 


o       o""*'"o"""""o" 


•s 

c 


NCOCQDS-^   Ttl^ 

o"       o" 


*i— I      Or-nC-^HN 


i  1 1 1 1  1 7 7 1 1  TTTTi  i  1 77 1  77777  77777  71  '  '  ' 


12 


CHAPTER  1.  AIR,  WATER  AND  STEAM 


D 

I 

u 

i— r 

I 


THO>iCOH5      iHOWN-OQ      00-^P^O      OOO»-IN.      NOOCC05W5      OOt-f^-CC      r-MCS^O 

Of«iocoo     OO»COQOOO     «ocooooco     coF-ioooeo     IHOOOCCH     OO^T-IOS     o^i-icsP 

M  M  i  M  i  ii  MM?  77777  77777  77777  77777 


Oi-HO      O^OiCOOO 


OCfio        OOOSOS 

SSSgS   §S§ 


33383     8  S8SSS  22222  25555  SSSSSS  SSS« 

M  M  I      M   M   I      M  M  I      M  M  I      MM!      M   M  I      MM! 


W 
-BSJ 

z$ 


•si 


t      tOOSr^^CO      ON^b-OJ      C^^*t-OSN      •*  N  OS  N  •* 
eOCQCOCQ^t      ^i^l^JiOiO      iSiOOCOO      Ob-l>Nt^      000000000      00000 

OJC5CJCSC5    ciciacJoi    cscJoicioi    oodo'oi    oioio'cicj    cJcicioos     oioioo'd 


eoweoeo^j 

CRC&OO5O5 


O3O>0>0>0) 


x^ 

s 

<; 


00000      OOOOC 


3g   §§§SS 


ggS^   2feS2S   §g§?2   £§2fc2 

«>>«!0       NWOOOO       NuaoOrHlO       OQ«C$TH«P 


t^^osmt-i     ocQ1^eo^ 
o^2c5c§     ^SSooo 


ON      OOCO"#t-O      00  tC 


8SSS8 


i-i  *n  co  IH  r*. 

TjtCSiOi-Hb- 


OikCt*-b-CO      i-i<MiCT-liO      CO  >O  OTIC1 

o*  o*  o" 


H^H        OSOOOI> 


tooao         ino 


s 

BE 


fi-<*CC(NiH      OOOOt-CO      iC-gCONiH      OOOOt-CD      kfl-^CONi 
^OO5O>C5      9^00000000      00  00  00  00  00      OOlSt^C^t**      C>S»t>»l>J 

Mill      I  M  I   I      I   I  I  II      Mill      II   I   I 


iC500t»-eo     iftjgwNtH 
MM      I  I   I   I   I 


•a 


13 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 


'53 


-?0«5»-i?? 


Ot-       <P«^M?i 


5.  s      $§3§£R   5s2£S3   S3&38   «S8S§5   SSSSS   33883   S&SS8 

6s"1" -2          '^W-*    -r-**-.i-<{-.i    -.,',_!  ,H',_I,^    o'ddcJos    doscsoooo    oooot>b»i>    b-cocooco 

£=£     ^^^^2  y^J^^1  ^-<^^^  ^^-r^  i    i  i  i  i  i    i  i  i  i  i    i  i  i  i  i 


Ed 

I 


3 

&& 

9«-* 

r°s 

*2J 


§|ll   sis's's'  s's'ss's"  s'ssss  sssss  s'ssss  sssss  sssss 


I 


— •  £*          I  QQSOO      OC5OOO      OG3C3OO       OCSOOO      OOOOO      OOOOO      OOOOO 
v.j£j  I  SSSSS       SSSSrH      ^rtS^S       S^THiHTH       tHiHi-lrHiH       ^r^iHrS^-l       rH rH rH i-( i-l 


R 


"g      i  ^Ji^^S     «N?IN«     OJSOWOTW     §^-**S    wSooS    t*ooooa 
'£      id"""'    o"  c  d  d  d 


COCCCC^HlO 

oco-*t^co 


occwcoeo     -*- 


i  !  ^ 

i,il 


1 


a 
I 


o  o  o  o  o  o  o 


O 

3 

tt 


ll 

so  v 


Q  M  T*  iH  |>       NOOOOW 

-- 


OOOO 

o»io£-« 


OO>OOSC5      OC5O 

eoeow^t^     CBcot 

rt<tOOb>00      O'-H 


MC4C4        C4C4COCQC 


S§§8   SS 
9^9   J3« 


s 
£ 
i 


I 


'o     §®^^*     I§^^^^J     ®wc§D3W     wwoiSco 

Mill     i i i  f i     i i i i i     i i i i i     i i i i i     i i i i i    TTTTT 


14 


CHAPTER  1.    AIR,  WATER  AND  STEAM 


i 

u 


I 

^ 

O 

H-3 


H 

I 

Q 
H 

H 
C/} 


"•SJ 

53 

«"sr"" 

f.  ^  00^ 
1C  rH  t»  (M  t>-       rH-tf  U500r^       t>00)OCO       t>j  O  O  i-i  b-       §§3^§*       £•> 

n 

"i 

=  3 

MM       Mill       1   1    1   1    1       IMIS       1    M  -H+    + 

1 

O^OCOOO       Clt-rHOO       OO^OOfO       !>CNOi-tiO       O"tC5COCO       W 

1 

1 

^1 

1 

6 

1 

.g 

S 

1 

-2 

MM       Mill       MM!       1   1    1   1    1       M    M    1 

o 
-So? 

•sH 

,Q.i 

?^ 

Vapor  to 
Saturate  it 

t-l  i-<  iH  T-l  «H        r-l  r-l  »-(  i-l  »-<        i-l  rH  iH  r-l  rH        r-l  ?H  r-l  r-t  r-4        r-H  »-H  rH  r-<  i-l        tH 

VOLUME  i 
BAROMETER,  1 

t 

- 

<4 

3  .ft 

5  •< 

3» 

»Ot-OOJ»O       t^OCO»OOO       OCO^OOOO       COiOOOOCC       tS^SSS       § 

OOi-liHi-l        T-tr-lr-lTHT-t        i-ti-lr^i-l»H        ^  '"I  rl  ^"1  ]^        Zlllllllr2!l3        2 
^  ,H  »-<  TH  r-l        rH  rH  r-<  i-H  rH        r-t  iH  r-(  iH  rH        i-H  rH  »H  rH  »H        r-l  rH  r-l  i-t  ri        r-i 

Q 

J 

O 

Illil         11111  Ilili  llill  1 

1 

•s 

jQ 

fi 

OOOCO(NO        lCr-nOCN*O        TfOOOO1^        QOOO»OOO1        Sfeo§S        S 

e  - 

.S 

illl  IIIII  IIIII  Hill  IIIII  I 

1 

53 

o 

o  "  '   "  '     o"   "  "   '   "     o  *  "   *  '     o"  *  *  '   *     o"                  o 

0 

fi 

TH^NNW       NWNNoi       CO  CO  CO  CO  CO       -*^^-*O       iOo"iO«D«       O 

§ 

ss 

OOOOO'O       OOt-'OOOO       t»  ^1  lO  iO  rH       CDOOOOCO       U5  ?O  SO  CO  *O       CO 

I- 

I 

illli  sllSS  lllSi  ISill  liiii  i 

'Jx 

^ 

§« 

s  2 

W 

<«                   o                   o                  o                   o                   o 

M 

rM 

s 

1 

-4 

^777  77777  77777  71  '  '  '    '  '  '  '  ' 

15 


HEATING   VENTILATING   Am  CONDITIONING   GUIDE  1938 


WNOJ101>       COMCOOSCO 


H     ' 

Ez, 


:iltl 


«*  00  i-*  CO  ®       OS  »-l  T*<  t«»  OS       (M^OO 

oooooseo     ooooo     »H»HIH 


ac  o  M  *c  DO     oro»cooo     cooooi-^co     oooococo     OOT-HCOCDOO     »-<eocooor-i     co«ooo»-ieo 

'  SfflSSOO      fc-fr-Nb-OO      OOOOOOOO       CSCSOOO      OtH^rH»H       <NCNJ(M(NCO       CO  CO  CO  Tfl  Tt< 

''  * "  * 


5O?*!*-      NOOOCO      00>O»CCO 
*  r-i  rf  !>•      T-n-'JOOCOl^      »-*  O  *H  CO 


'-uncCCOS-      lOb-'tHC 
Ol>»OCOiH       OCSCSO 


OiHN       ^uOcDtOO 


OC^t'-'H—       i-itN.cqoo-* 


i-HOiOCOO       M  CO  1C  t- CO      rt<Oi-iCO<Q       <MCO*-tCOCO       0>  i-H  i-H  r-i  T* 
>-i  )>  id  (N  O       CO  CO  »O  **  -*       ^  UO  CO  1>  OS       <M  »O  Oi  CO  00      COOt-OOOS 


!E!  I    ii§S8S  Si 


c^ 
u* 
c 


I  -"  '  r-(C5!?3 

III  «    13! 


b-2 


O(M       OrJHO^O       (M  (N  O  Tt*  >O 


-•*iHflj 
tllOCOCO 


1>THO51OCO  »OOOlM»Ot^ 

T^COCOCOr^  ii5N-T^"^Ol 

I>iOrhMlN  NCMCO^lO 

b«OOO5OrH  -  iMOQTfllOO 


i 


i-l       NiHXOi-i       COOO50CM       OiOOOrH 

- 


iiS 


ssiss. 


5D  I  J>t^OOO-*  OO^r-IOSOO  C35r-(«OOl>  CD  CO  O5  CO  OS  OOOONCO-*  rH  CO  C 

£3  jr-CJrHTT'CO  OOi— I«*COCS  N  CO  O5  CO  CO  O  ^  00  CO  t*«  C^b»COOO'Tl  O  CO  C< 

•5  jSSoSS  SSS§g  oooo^  8SS8S  SSSSS  $2S2^ 

s  i  °  P  o"    '    '    "    "  O*    "    "    "    '  O*    "    *    *    *  O* 


. 
^CMOl>*O 

COI>OOOOOS 


16 


CHAPTER  1.   AIR,  WATER  AND  STEAM 


Q 
W 
D 
2 


O 

u 


3 


o^oow        weocqiH  tHw^sco  "iooooo  icr-o^o  r-o«ooo»-i  owiH»-ieq 

OS  "<Ji  00  Ofl  t*  »-ieOiHCOiH  ?0iHtOi-U>  <N  00  COOS"?  »-i  t»  ^)  O  t*  cCOt*-rt<Cl  Osf»»OCO*-i 

cqcOOQ^Tl*  lOUiCOtOtS  b«OOOOOSOJ  OOHi-iN  CCCOriiUtSiO  eSt^t^OOQ  OOiHCQM 

rt^iHiHrH  ^rtrHrtrt  M  rl  rH  rt  rl  <N  <M  N  (N  N  <N  N  «  d  W  <NN<NN<N  NCOCOCOCC 


CO  CO  00  f^  CO      USOOOWO 

oooocooici     csaso'o'd 


QOON-i-iiO      OCOt^iHUi      CSC 
S<N^b-GS      iiTjisOOiiH      Wt 


o 
>O 


Sl^OCOO  OsWOOOiH  tKI>OCOCO  OS<NtOO(N  IOO5 

>COCO(O  Ot^t^t^OO  OOOOC5OO5  OOOO«-i  i-trHC 

WNNNN  NNWNN  WNNDJCQ  dCCMCOCC  COCOMCOCO      CCCOWCOW       eOWCCCOCO 

pHrHi-^THf-H  ^H  iH  TH  T-l  r-l  rHrlfHiHrH  iH  rl  rH  r-l  i-H  i-l  r-(»H  iH  i-H       iH  i-l  i-(  iH  T-t       1-(T-HHtHi-H 


s 


a 

i 

Q 

w 

H 


P-. 

CD 


5i-l      WONOSrH      T}icCOJT-c*      t"-OWOOS      (NU3CSNO 

mo     io»ftioioo     ooot^t^    t-ooooooco     osoooo 


I 


i«o     T^t-noc 


Boo  ooooo  ooooo 


eoeoeoeoco 


Ot-      CSN^h 


o"3O£iO 
SOOOi-i 

8888 


I 

!I 


w 
•s 

c 


OIOC 


NC^lNlNfN 


Hi-4CO^Ot«      iHiOi-^OCO      OOBOOQOO      C\)U5 

O  CO  CO  CO  CO       CO  CO  CO  ^  ^       •^•^•^•^lO       lOiQU 


s 
^ 


IACOt*OOQ      Oi-i(NOOTjH      tOOb-000)      e«H 

woocoeoco     ^^««t<-^^     ^<^^^^    ujio 


HEATING  VENTILATING  Am  CONDITIONING  GUIDE  1938 


g     g      j  I>SIO»MIS     c^sswoo     CTr*i-«eo     »oo~*«ooco     r^NOrsio     o-^csccoo 

''  '' 


I  ;SII11  SSSSS  SSSSS   SS'SS 

\      **     'S  ;  COOCO        COCOO        OOOOO        OOOOO        O*Hi-HtHr-l        fHiHiHiHi-4        ,-HHiHTH 


5   ' 


js  i 


=1       u=: 
'.        £« 


""t* 

~<I 

*& 


rf  i  "J 


H     i 

i! 

<  ;     s 
>       £ 


^•^(Nt-^C 
U3  Q5b»OOC 
WIN  (N  CMP 


I          «        '    ' 


I 


' 


c  I 


SSfeSS  b^^6;*  ooSw^^  5§S 
^g^^g  £§£££  Sgggg^  «S 


S8888  88888  88888  888ii  lilil  Illli  §§§§§ 

®  °  o  o  X  "   *  "  "    M    •••••••.. 


SS 

o«e»^«  «W!»s  isssfe  gggss  g 


TJJ3J52GSN     5*t« 

00  00  OOOOO)      OO 


18 


CHAPTER  1.  Am,  WATER  AND  STEAM 


I 


fij 


3    a 


2QCOO«*       «O»HOGCD      OCOWOO      OSrHNMeO       CO'Ht'-.O 
OiHOQio     ooc*t<-o4r»     TjHrHosoooo    QOOMOO     xaoioooo 


fflOI>b-oO      OooOS 
OOOOO       OOO 


rtua     OTJHOSOOOO     wt 

OO      ^*tHtHoJoiJ      COC 
rt^iHi-lrH       iH  i 


N«cOi-no 

NOOOOOSoi 
i-t  T-l  rH  iH  1-1 


*i 
£s 
58 


i 


^^Or*'*      iHOOWCOO      OOCOrticq»-«      OOOQONr>-      OOt*.t^OO      OiHCOiOh.      O0 
03^10*0(0       t-t-WOJO      O^NCO-*      10 10  Ot*  00      0»  Oi-4C4  CO       TPOI>OOC>       rH 

iflifstouso    ?c5o«o«oo    (O«o«odt3     <ONNt^»^    Nlt^t^t^i^    0606000606 


OW      iOh-O5CM»O      t-pCM«3t*.      OWiCl^O      NO 
CO  CO      COCOCOTJI^      ^QiO>0>Q      OOOOt*      t^b- 


lOr-iQ        ^MND 


eOrfrH 


o 

•5 


OCCDDCO      COWSOC 


cotoocQcr 

OOiHlOfHC 
b.t>COCOCC 


oo«5^c< 
ptcouibo 


rH*OOS"5CO       i-tr-tCi 

3*»SP«     wgor 


•3 

a 


oeoeoweo    co  coco  coco 


s 
gt 


a 

s 


HEATING  VENTILATING   AIR  CONDITIONING   GUIDE  1938 


a 

5 
g 

N 
Z 


& 

< 


&&* 


c 

H 

fc* 
O 

pf 
< 

? 

& 


> 


^ 

1 

tf 

D 
H 


fa 
O 


£§!"'  JSS5 


£33S  SS38S  3SS8S  SSSSS  35323  35353 


S.*6*  2      '  *a  pi  *»  *<9  •*     **•*»(*  is*  «s    OI^N-OOOO     essscsoo 
jsSJja      I  ?J?<5'5MS    MNWN??    tjNNww     WNNCOM 


§  ;*-»*••:  ss  re  i-  ^ 

-2  c.*^s?u's  ^.  . 

!^  !  rcw»f •»*-*  ^jJujttiiius  occcotoo     i^h^t^boo 

H  CCSCWMC?  -cwwccw  rtccwccec     coMcoroeo 


csoi-<»-     iHi- 

(N  «N  <N  (N  N       OTN 


I       "*  j? 


ie  15  us  in  is 


>OQOOMU3  OOPMOOO  i-tCO5OQO»H  COeOOOr-ieO  COOO«HCO«O 

WMn4T}J^4  ^jSSiOioSS  tfSCOOOb-  N-fr-lNOOOO  OOOOO»»O 

i^'iftL'iiflio  iQto'ioia'to  loioiousio  10  us*  us  us*  us  toioioioio 

rHr-liHi-li-l  ,H  rH  »H  iH  i-l  iH  »-4  »H  ^1  i-t  ^^Hrt^HH  rH  i-l  iH  iH  T-( 


I 


K 

g 


j2 


s 


ooo»osoo«o 

OCOiH^Ici 


OlOiHN-*       lOOOOOir-l       N-t 
NCCCOWS       MMOOM^       ^r 

o*  o*  o" 


iHOS»-tN.eO 
CO*-iCOOiO 


oooooseo     soi-io»-(t 


S  ooooo  ooooo  Soooo  ooooo  ooooo 


Ilill 

coeo'cocooo 


looooo    oo'h'f.V*    N.Vb."oo"oo     ooooooos'os"     ojoooo     o^*4rtj4     nnneoeQ 


sssss 


20 


CHAPTER  1.   AIR,  WATER  AND  STEAM 


Q 
W 
Q 

I 


5 

i 
g 


£ 


8 

ta 

o 


I 

rt 

I 

Q 


g 
I 

co 

w 
n 


5s 


S 
I 


& 


QiHOiH  ij*  OJ  t*  00  »•* 
OONS  OOiHiftO-^ 
Ocpr— r»  r- 00  00  00  O 


O<^a»COOO       04 


00 1-1  COO  00       I-H  CO  CO  00  i-l       OQCOOQv-l-44       CD  O5  »-!•<#  CO       Or-C^COO       *-< 
C3JOOOO       iHiHiHiHM      (N  CNN  CO  CO      COCO^-*-*       r!J>O»O»O«O       «o 

lAcdcococo     co  cd  co*  «o  co*     ed  co  co  co  CD     co' co*  co' co  co*     co'co'co'coco     co* 


«OCOOJWU5      b-iOb-b-OO      eOiH-^i-105      OOOOO      OOOOO      O 


O  O"  O     "     "     "rH       r^T^rHiHiH 


iQoooe 


t-i^H^fHtH       T-KNCQCvKN 
CDOOOO      OOOOO 


SiH       CO  Is- I-H  t>. 


0001-1^     »-* 


I 


10 10  to  «0  to     ivi>»oooo    asasos 

-         -     -         -  -          -- 


HEATING  VENTILATING   AIR  CONDITIONING   GUIDE  1938 


Via  (Wv  -  W)  =  c^  (t  -  *')  +  c»sW  (t  -  *')  (9a) 

and  using  cPa  «  0.24  and  c^  =  0.45 

fcff8  (Wti  -  WO  -  (0.24  +  0.45J7)  (/  -  *•)  (9b) 

where 

A!fg  «  latent  heat  of  vaporization  at  t\  Btu  per  pound. 

(Wt*f—  W}  =  increase  in  vapor  associated  with  1  Ib  of  dry  air  when  it  is  saturated 
adiabatically  from  an  initial  dry-bulb  temperature,  tt  and  an  initial  vapor  content,  W. 
pounds. 

Knowing  any  two  of  the  three  primary  variables,  t,  t',  or  W,  the  third 
may  be  found  from  this  equation  for  any  process  of  adiabatic  saturation. 

TOTAL  HEAT  AND  HEAT  CONTENT 

The  total  heat  of  a  mixture  of  dry  air  and  water  vapor  was  originally 
defined  by  W.  H.  Carrier  as 

S  -  c^(t  -  0)  +  W  [A'fg  +  c^(t  -  /')]  (10) 

where 

S  =  total  heat  of  the  mixture,  Btu  per  pound  of  dry  air. 
£pa  ™  raean  specific  heat  at  constant  pressure  of  dry  air. 
Cpg  —  mean  specific  heat  at  constant  pressure  of  water  vapor. 
/  =  dry-bulb  temperature,  degrees  Fahrenheit. 
t1  =  wet-bulb  temperature,  degrees  Fahrenheit. 

W  =  weight  of  water  vapor  mixed  with  each  pound  of  dry  air,  pounds. 
#fg  =  latent  heat  of  vaporization  at  t1,  Btu  per  pound. 

Since  this  definition  holds  for  any  mixture  of  dry  air  and  water  vapor, 
the  total  heat  of  a  mixture  with  a  relative  humidity  of  100  per  cent  and  at 
a  temperature  equal  to  the  wet-bulb  temperature  (/')  is 


By  equating  Equation  lOto  Equation  11,  the  equation  for  the  adiabatic 
saturation  process,  Equation  9a,  follows.  This  demonstrates  that  the 
adiabatic  saturation  process  at  constant  wet-bulb  temperature  is  also  a 
process  of  constant  total  heat.  In  short,  the  total  heat  of  a  mixture  of  dry 
air  and  water  vapor  is  the  same  for  any  two  states  of  the  mixture  at  the 
same  wet-bulb  temperature.  This  fact  furnishes  a  convenient  means  of 
finding  the  total  heat  of  an  air-vapor  mixture  in  any  state. 

Enthalpr 

T,  J?iS  to.tal.heat  of  J^  air-vapor  mixture  is  not  exactly  equal  to  the  true 
heat  content;or  enthalpy  of  the  mixture  since  the  heat  content  of  the 
liquid  is  not  included  in  Equation  10.  With  the  meaning  of  hea?  content 
m  agreement  with  present  practise  in  other  branches  of  liermodynamics 
the  true  heat  content  of  a  mixture  of  dry  air  and  water  vapor  (SthTp 

?oSr  ?he  S&ol^  and  the  "^^  ***  at  32  F  «  tie  datum 


22 


CHAPTER  1,   AIR,  WATER  AND  STEAM 


h  «  cPa  (t  -  0)  -f  W  h9  =  0.24  (*  -  0)  +  W  ks  (12) 

where 

h  —  the  heat  content  of  the  mixture,  Btu  per  pound  of  dry  air. 
t  =  the  dry-bulb  temperature,  degrees  Fahrenheit. 
W  =  the  weight  of  vapor  per  pound  of  dry  air,  pounds. 
hs  =  the  heat  content  of  the  vapor  in  the  mixture,  Btu  per  pound. 

The  heat  content  of  the  water  vapor  in  the  mixture  may  be  found  in 
steam  charts  or  tables  when  the  dry-bulb  temperature  and  the  partial 
pressure  of  the  vapor  are  known.  Or,  since  the  heat  content  of  steam  at 
low  partial  pressures,  whether  super-heated  or  saturated,  depends  only 
upon  temperature,  the  following  empirical  equation,  derived  from  Proper- 
ties of  Saturated  Steam  by  J.  H.  Keenan,  Table  8,  may  be  used: 

hs  -  1059.2  +  0.45  /'  (13) 

Substituting  this  value  of  h&  in  Equation  12,  the  heat  content  of  the 
mixture  is 

h  =  0.24  (t  -  0)  +  W  (1059.2  +  0.45  *!)  (14) 

Example  5.  Find  the  total  heat  of  an  air-vapor  mixture  having  a  dry-bulb  tem- 
perature of  85  F  and  a  wet-bulb  temperature  of  70  F. 

Solution.  From  Table  6,  for  saturation  at  the  wet-bulb  temperature,  W£  =  0.01574, 
and  from  Equation  14, 

h  =  0.24  (70-0)  +  0.01574  [1059.2  +  (0.45  X  70)]  =  33.96  Btu  per  pound  dry  air. 

By  considering  the  temperatures  in  Table  6  to  be  wet-bulb  readings,  the 
enthalpy  of  any  air-vapor  mixture  may  be  obtained  from  the  last  column 
in  the  table. 

An  energy  equation  can  be  written  that  applies,  in  general,  to  various 
air  conditioning  processes,  and  this  equation  can  be  used  to  determine  the 
quantity  of  heat  transferred  during  such  processes.  In  the  most  general 
form,  this  equation  may  be  explained  with  the  aid  of  Fig.  1  as  follows. 

The  rectangle  may  represent  any  apparatus,  e.g.,  a  drier,  humidifier,  dehumidifier, 
cooling  tower,  or  the  like,  by  proper  choice  of  the  direction  of  the  arrows. 

In  general,  a  mixture  of  air  and  water  vapor,  such  as  atmospheric  air,  enters  the 
apparatus  at  1  and  leaves  at  3.  Water  is  supplied  at  some  temperature,  &.  For  the  flow 
of  1  Ib  of  dry  air  (with  accompanying  vapor)  through  the  apparatus,  provided  there  is  no 
appreciable  change  in  the  elevation  or  velocity  of  the  fluids  and  no  mechanical  energy 
delivered  to  or  by  the  apparatus, 

h  +  £h  +  (W,  -  W,)  A,  =  h,  +  Re 

or 

Eh  -  RC  -  h,  -  A,  -  (W,  -  W,)  A,'  (15) 

where 

Eh  =  the  quantity  of  heat  supplied  per  pound  of  dry  air,  Btu. 

RC  —  the  quantity  of  heat  lost  externally  by  heat  transfer  from  the  apparatus. 

Btu  per  pound  of  dry  air. 

Wi  =  the  weight  of  water  vapor  entering,  per  pound  of  dry  air. 
Wz  —  the  weight  of  water  vapor  leaving,  per  pound  of  dry  air. 
}i*  =»  the  heat  content  of  the  water  supplied  at  h,  Btu  per  pound. 


HEATING  VENTILATING  AIR  CONDITIONING   GUIDE  1938 


Aa  —  hi  =  the  increase  in  the  heat  content  of  the  air-water  vapor  mixture  in  passing 
through  the  apparatus,  Btu  per  pound  of  dry  air 

-  0.24  (/,  -  ft)  +  Wi  (1059.2  +  0.45  /»)  -  Wi  (1059.2  +  0.45fc) 

The  net  quantity  of  heat  added  to  or  removed  from  air-water  vapor 
mixtures  in  air  conditioning  work  is  frequently  approximated  by  taking 
the  differences  in  total  heat  at  exit  and  entrance. 

For  example,  in  Fig.  1,  an  approximate  result  is 

£h  -  -Re  =  Sa  -  Si  (16) 

where 

Sj  «  the  total  heat  of  the  air- vapor  mixture  at  exit,  Btu  per  pound  of  dry  air. 

Si  ••  the  total  heat  of  the  air-vapor  mixture  at  entrance,  Btu  per  pound  of  dry  air. 


Wi  Ib,  Water  Vapor 
lib.  Dry  Air 


W3  Ib.  Water  Vapor 
lib.  Dry  Air 


r?r 

<W5-H$)lb.  Water 

FIG.  1.    DIAGRAM  ILLUSTRATING  ENERGY  EQUATION  15 

From  the  definitions  of  total  heat  and  heat  content,  it  may  be  demon- 
strated that  Equation  16  is  exactly  equivalent  to  Equation  15,  when,  and 
only  when,  t\  =  t\  =  fa;  i.e.,  when  the  initial  and  final  wet-bulb  tempera- 
tures and  the  temperature  of  the  water  supplied  are  equal.  The  one  pro- 
cess that  meets  these  conditions  is  adiabatic  saturation,  and  either 
equation  will  give  a^result  of  zero;  for  other  conditions,  Equation  16  is 
approximate  but  satisfactory  for  many  calculations. 

The  following  problems  illustrate  the  application  of  these  principles: 

&cample  6.  Heating  (data  from  Example  2).  Assuming  the  water  to  be  supplied  at 
60  F,  the  net  quantity  of  heat  supplied  is,  from  Equation  15, 

£h  -  Re  -  0.24  (70  -  0)  +  0.000548  X  0.45  (70  -  0)  +  0.005632 
[1059.2  +  0.45  X  70  -  (50  -  32)]  -  22.90  Btu  per  pound  of  dry  air. 

Cooling  (data  from  Example  3).    If  the  condensate  is  removed  at  54  F 
— *  removed  is  found  from  Equation  15,  by  proper  regard  to  the  arrow 


£fa  +  #c  -  0.24  (84  -  54)  +  0.00887  X  0.45  (84  -  54)  +  0  00361 
[1059.2  +  0.45  X  84  -  (54  -  32)]  -  11.  24  Btu  per  pound  of  dry  air. 

«*«->  —  the  wet-bulb 

fr°-m  ^K6'  since  **  «£t  air  is  saturated,  22.55  Btu  per 
quantity  of  heat  removed  is,  approximately 

f  dry  air<  The  degree  °f  appr-mat-  ^ 


24 


CHAPTER  1.   AIR,  WATER  AND  STEAM 


PSYCHROMETRIC  CHART 

The  revised  Bulkeley  Psychrometric  Chart4,  will  be  found  attached  to 
the  inside  back  cover.  It  shows  graphically  the  relationships  expressed 
in  Equations  9a  and  9b.  It  also  gives  the  grains  of  moisture  per  pound  of 
dry  air  for  saturation,  the  grains  of  moisture  per  cubic  foot  of  saturated 
air,  the  total  heat  in  Btu  per  pound  of  dry  air  saturated  with  moisture, 
and  the  weight  of  the  dry  air  in  pounds  per  cubic  foot.  Fig.  2  shows  the 
procedure  to  follow  in  using  the  Bulkeley  Chart.  The  directrix  curves 
above  the  saturation  line  are  as  follows: 

A  is  the  total  heat  in  Btu  contained  in  the  mixture  above  0  F,  and  is  to  be  referred 
to  the  column  of  figures  at  the  left  side  of  the  chart.  Heat  of  the  liquid  is  not  included. 


A,  B,  C,  D,  E,  FaDirectrix  lines 
D.  B.  L»Dry  bulb  line 
D.  P.  L=Dew  point  line 


R.  H.  L=Relative  humidity  line 
W.B.1_=  Wet  bulb  line 
Sl=  Saturation  line 


G.  P.  Lb»  Grains  moisture  sat  mixture  per  Ib  dry  air  R.  D.  D.  S.=  Relative  density  dry  air  per  cu  ft  saturated 

T.  H.=Total  heat  sat  mixture  per  Ib  dry  air  W.  P.  C.  F.  S.=  Weight  per  cu  ft  in  Ibs  saturated 

V.  P.»Vapor  pressure  in  mm  mercury  R.  D.  S.*Relative  density  per  cu  ft  saturated 

G.  P.  C.  F.  S.=Grains  moisture  per  cu  ft  sat  air  W.  P.  C.  F.  D.»  Weight  per  cu  ft  in  Ibs  dry 

W.  D.  A.  C.  F.  S.=Weight  dry  air  per  cu  ft  in  Ibs  saturated  R.  D.  D.=Relative  density  per  cu  ft  dry 


W.  P.  C.  F.  x 
R.  D.x 


-  w-  p-  c-  F-  *  parta'  MturaBon 


FIG.  2     DIAGRAMS  SHOWING  PROCEDURE  TO  FOLLOW  IN  USING  BULKELEY  CHART 

B  is  the  grains  of  moisture  of  water  vapor  contained  in  each  pound  of  the  saturated 
mixture  and  is  to  be  referred  to  the  figures  at  the  left  side  of  the  chart. 

C  is  the  grains  of  moisture  of  water  vapor  per  cubic  foot  of  saturated  mixture,  and  is 
to  be  referred  to  the  figures  at  the  left  side  of  the  chart  which  are  to  be  divided  by  10. 

D  is  the  weight  in  decimal  fractions  of  a  pound  of  dry  air  in  one  cubic  foot  of  the 
saturated  mixture,  and  is  referred  to  the  first  column  of  figures  to  the  right  of  the  satura- 
tion line  between  the  vertical  dry-bulb  temperature  lines  170  and  180  F.  The  relative 
density  of  the  mixture  is  read  in  a  similar  manner  from  the  same  curve  by  the  column  of 
figures  between  the  vertical  dry-bulb  temperature  lines  180  and  190  F. 

E  is  similar  to  D  but  is  for  one  cubic  foot  of  the  saturated  mixture. 


«The  Bulkeley  Psychrometric  Chart  was  presented  to  the  Society  in  1926.    (See  A.S.H.V.E.  TRANS- 
ACTIONS, Vol.  32,  1926,  p.  163.)    Single  copy  of  the  chart  can  be  furnished  at  a  cost  of  $  .25. 


HEATING  VENTIUITING  AIR  CONDITIONING   GUIDE  1938 

F  is  similar  to  D  but  is  for  dry  air,  devoid  of  all  moisture  or  water  vapor.  For  con- 
venience, the  approximate  absolute  temperature  of  500  F  is  given  at  40  F  on  the  satura- 
tion line  for  the  purpose  of  calculating  volume,  weight  per  cubic  foot,  and  relative  density 
at  partial  saturation. 


METHOD  OF  USING  THE  CHART 

Relati 

__., line,  t 

as  46  per  cent. 


Example  8.  Relative  Humidity:  At  the  intersection  of  the  78  F  wet-bulb  line  and  the 
95  F  dry-bulb  line,  the  relative  humidity  is  read  directly  on  the  straight  diagonal  lines 
as  46  per  cent. 

Example  9.  Dew  Point:  At  the  intersection  of  the  78  F  wet-bulb  line,  the  dew-point 
temperature  is  read  directly  on  the  horizontal  temperature  lines  as  70.9  F. 

Example  10.  Vapor  Pressure:  At  the  intersection  of  the  78  F  wet-bulb  line  and  the 
95  F  ^dry-bulb  line,  pass  in  a  horizontal  direction  to  the  left  of  the  chart  and  on  the 
logarithmic  scale  read  the  vapor  pressure  as  19.4  millimeters  of  mercury.  (Divide  by 
25.4  for  inches.) 

Example  11.  Total  Heat  Above  0  F  in  Mixture  per  Pound  of  Dry  Air  Saturated  with 
Moisture:  From  where  the  wet-bulb  line  joins  the  saturation  line,  pass  in  a  vertical 
direction  on  the  78  F  dry-bulb  line  to  its  intersection  with  curve  A  and  on  the  logarithmic 
scale  aMhe  left  of  the  chart  read  40.6  Btu  per  pound  of  mixture.  The  use  of  this  curve 
to  obtain  the  total  heat  in  the  mixture  at  any  wet-bulb  temperature  is  a  great  con- 
venience, as  the  number  of  Btu  required  to  heat  the  mixture  and  humidify  it,  as  well  as 
the  refrigeration  required  to  cool  and  dehumidify  the  mixture,  can  be  obtained  by 
taking  the  difference  in  total  heat  before  and  after  treatment  of  the  mixture. 

Example  12.  Grains  of  Moisture  per  Pound  of  Dry  Air  Saturated  with  Moisture: 
From  70.9  F  dew-point  temperature  on  the  saturation  line,  pass  vertically  to  the  inter- 
section with  curve  B  and  on  the  logarithmic  scale  at  the  left  read  114  grains  of  moisture 
per  pound. 

Example  1$.^  Grains  of  Moisture  per  Cubic  Foot  of  Mixture,  Partially  Saturated:  From 
/0.9  F  dew-point  temperature  on  the  saturation  line  proceed  in  a  vertical  direction  to 
curve  C,  and  on  the  logarithmic  scale  to  the  left  read  83.3  which,  divided  by  10  gives 
S.d3  grains.  A  temperature  of  70.9  F  is  equal  to  an  absolute  temperature  of  530.9,  and 
95  F  equals  555,  absolute  temperature.  Therefore,  ^  x  8>33  .  7  97  gr^n&  pcf 
cubic  foot  of  partially  saturated  mixture. 

Example  14.  Grains  of  Moisture  per  Cubic  Foot  of  Saturated  Air:  Starting  at  the 
saturation  line  at  the  desired  temperature,  pass  in  a  vertical  direction  to  curve  C  and  on 
the  logarithmic  scale  at  the  left,  read  a  number  which,  divided  by  10,  will  give  the 
answer. 

Example  IS.    Weight  per  Cubic  Foot  of  Dry  A  ir  and  Relative  Density:   From  the  point 

±^rr3mTKe'vhe  1?  F<  vertical  dry'bulb  Iine  intersects  curo  £-  Pass  to  rightP°  We 
and  read  0.075  Ib;  if  cubic  feet  per  pound  are  desired,  divide  1  by  this  amount  The 
relative  density  is  read  immediately  to  the  right  as  1.00.  <"«UUni.  me 


i"  per  C^Foot  °f  Saturated  Mixture  and  Relative 
Vn  t     r,v  '-f°r  exafflP'e,  the  70  F  vertical  line  intersects  the  curve 

£  £4,7"*  per  cublc  foot  as  °-07316 


Partially 

si 


Therefore,  ^  =  0.851.  The  weight  of  1  cu  ft  of  air  at  50  F  dry-bulb  and  46  F  wet-bulb 

x  °'851  =  a°6675-  and  the  relative  dens*v  »  1-046 


26 


CHAPTER  1.   AIR,  WATER  AND  STEAM 


PROPERTIES  OF  WATER 

Composition  of  Water.  Water  is  a  chemical  compound  (H2O)  formed  by 
the  union  of  two  volumes  of  hydrogen  and  one  volume  of  oxygen,  or  two 
parts  by  weight  of  hydrogen  and  16  parts  by  weight  of  oxygen. 

Density  of  Water.  Water  has  its  greatest  density  at '39.2  F,  and  it 
expands  when  heated  or  cooled  from  this  temperature.  At  62  F  a  U.  S. 
gallon  of  231  cu  in.  of  water  weighs  approximately  8%  Ib,  and  a  cubic  foot 
of  water  is  equal  to  7.48  gal.  The  specific  volume  of  water  depends  on  the 
temperature  and  it  is  always  the  reciprocal  of  its  density.  (See  Table  7.) 

TABLE  7.    THERMAL  PROPERTIES  OF  WATER 


TEMPERATURE 
DEGF 

SAT.  PRESS. 
LB  PER  SQ  IN. 

VOLUME  Cu  FT 
raaLs 

WEIGHT  LB  PER 
CuFi 

SPECIFIC 
HEAT 

32 

0.0887 

0.01602 

62.42 

1.0093 

40 

0.1217 

0.01602 

62.42 

1.0048 

50 

0.1780 

0.01602 

62.42 

1.0015 

60 

0.2561 

0.01603 

62.38 

0.9995 

70 

0.3628 

0.01605 

62.31 

0.9982 

80 

0.5067 

0.01607 

62.23 

0.9975 

90 

0.6980 

0.01610 

62.11 

0.9971 

100 

0.9487 

0.01613 

62.00 

0.9970 

110 

1.274 

0.01616 

61.88 

0.9971 

120 

1.692 

0.01620 

61.73 

0.9974 

130 

2.221 

0.01625 

61.54 

0.9978 

140 

2.887 

0.01629 

61.39 

0.9984 

150 

3.716 

0.01634 

61.20 

0.9990 

160 

4.739 

0.01639 

61.01 

0.9998 

170 

5.990 

0.01645 

60.79 

1.0007 

180 

7.510 

0.01650 

60.61 

1.0017 

190 

9.336 

0.01656 

60.39 

1.0028 

200 

11.525 

0.01663 

60.13 

1.0039 

210 

14.123 

0.01669 

59.92 

1.0052 

212 

14.696 

0.01670 

59.88 

1.0055 

220 

17.188 

0.01676 

59.66 

1.0068 

240 

24.97 

0.01690 

59.17 

1.0104 

260 

35.43 

0.01706 

58.62 

1.0148 

280 

49.20 

0.01723 

58.04 

1.0200 

300 

67.01 

0.01742 

57.41 

1.0260 

350 

134.62 

0.01797 

55.65 

1.0440 

400 

247.25 

0.01865 

53.62 

1.0670 

450 

422.61 

.      0.01950 

51.30 

1.0950 

500 

681.09 

0.02050 

48.80 

1.1300 

550 

1045.4 

0.02190 

45.70 

1.2000 

600 

1544.6 

0.02410 

41.50 

1.3620 

700 

3096.4 

0.03940 

25.40 



Water  Pressures.  Pressures  are  often  stated  in  feet  or  inches  of  water 
column.  At  62  F,  with  h  equal  to  the  head  in  feet,  the  pressure  of  a 
column  of  water  is  62.383fe  Ib  per  square  foot,  or  0.433fe  Ib  per  square  inch. 
A  column  of  water  2.309  ft  (27.71  in.)  -high  exerts  a  pressure  of  one  pound 
per  square  inch  at  62  F. 

Boiling  Point  of  Water.  The  boiling  point  of  water  varies  with  the 
pressure;  it  is  lower  at  higher  altitudes.  A  change  in  pressure  will  always 
be  accompanied  by  a  change  in  the  boiling  point,  and  there  will  be  a  cor- 

27 


HEATING 

VENTILATING   AIR  CONDITIONING   GUIDE  1938 

TABLE  8.    PROPERTIES  OF 

Specific  Volume 
££/*!?&.  SS'F.       l££id     Erap.     V?^r 

p           t           Vf        Vfc       vg 

WH*     58.83       0.01603  1256.9    1256.9 

SATURATED  STEAM: 

Total  Heat 
Sat.                         Sat. 
Liquid     Evap.       Vapor 

hf         hfg        tr« 
26.88-    1058.8    1085.7 

PRESSURE  TABLE* 

Entropy 

Liquid      Evap.       Vapor  Lb./Sq.  JS£ 
8f      *      Sfg            Sg                p 
0.0533    2.0422    2.0955      WH* 

%"H&     70.44 

0.01605 

856.5 

856.5 

38.47 

10523 

1091.0 

0.0754 

1.9856    2.0609 

%"Hff 

l"Hj 

r     79.06 

0.01607 

652.7 

652.7 

47.06 

1047.8 

1094.9 

0.0914 

1.9451 

2.0365 

l"Hff 

V&"  Hi 

r     91.75 

0.01610 

4453 

4453 

59.72 

1040.8 

1100.6 

0.1147 

1.8877 

2.0024 

WHff 

2"H*   101.17 

0.01613 

339.5 

3393 

69.10 

1035.7 

1104.8 

0.1316 

1.8468 

1.9784 

2"  Hi 

2'4"Hfi 

r   108.73 

0.01616 

2752 

2752 

76.63 

10313 

1108.1 

0.1450 

1.8148 

1.9598 

2i/2;;Hff 

3"Hgr   115.08 

0.01618 

231.8 

231.8 

82.96 

1027.9 

1110.8 

0.1561 

1.7885 

1.9446 

1.0 

101.76 

0.01614 

333.8 

333.9 

69.69 

10353 

1105.0 

0.1326 

1.8442    1.9769 

1.0 

2.0 

126,10 

0.01623 

173.94 

173.96 

93.97 

1021.6 

1115.6 

0.1750 

1.7442 

1.9192 

2.0 

3.0 

141.49 

0.01630 

118.84 

118.86 

10933 

1012.7 

1122.0 

02009 

1.6847 

1.8856 

3.0 

4.0 

152.99 

0.01636 

90.72 

90.74 

120.83 

1005.9 

1126.8 

02198 

1.6420 

1.8618 

4.0 

5.0 

16225 

0.01641 

7339 

73.61 

130.10 

1000.4 

1130.6 

02348 

1.6088 

1.8435 

5.0 

6.0 

170.07 

0.01645 

62.03 

62.05 

137.92 

995.8 

1133.7 

02473 

13814 

1.8287 

6.0 

7.0 

176.85 

0.01649 

53.68 

53.70 

144.71 

991.7 

1136.4 

0.2580 

13582 

1.8162 

7.0 

8.0 

182.87 

0.01652 

4738 

4739 

150.75 

988.1 

1138.9 

02674 

1.5379 

1.8053 

8.0 

9.0 

18828 

0.01*656 

42.42 

42.44 

156.19 

984.8 

1141.0 

02758 

13200 

1.7958 

9.0 

10.0 

19321 

0.01658 

38.44 

3-8.45 

161.13 

981.8 

1143.0 

0.2834 

13040 

1.7874 

10.0 

11.0 

197.75 

0.01661 

35.15 

35.17 

165.68 

979.1 

1144.8 

02903 

1.4894 

1.7797 

11.0 

12.0 

201.96 

0.01664 

32.40 

3Z.42 

169.91 

9763 

1146.4 

02968 

1.4760 

1.7727 

12.0 

13.0 

205.88 

0.01666 

30.06 

30.08 

173.85 

974.1 

1147.9 

03027 

1.4636 

1.7663 

13.0 

14.0 

209.56 

0.01669 

28.05 

28.06 

177.55 

971.8 

11493 

03082 

1.4521 

1.7604 

14.0 

14,696 

212.00 

0.01670 

26.80 

26.82 

180.00 

9702 

1150.2 

03119 

1.4446 

1.7564 

14.696 

16.0 

21632 

0.01673 

24.75 

24.76 

18435 

967.4 

1151.8 

03184 

1.4312 

1.7496 

16.0 

18.0 

222.40 

0.01678 

22.16 

22.18 

190.48 

9633 

1154.0 

03274 

1.4127 

1.7402 

18.0 

20.0 

227.96 

0.01682 

20.078 

20.095 

196.09 

959.9 

1156.0 

03356 

13960 

1.7317 

20.0 

22.0 

233.07 

0.01685 

18363 

18380 

20125 

956.6 

1157.8 

03431 

13809 

1.7240 

22.0 

24.0 

237.82 

0.01689 

16.924 

16.941 

206.05 

953.4 

11593 

03500 

13670 

1.7170 

24.0 

26.0 

242.25 

0.01692 

15.701 

15.718 

210.54 

950.4 

1161.0 

03564 

13542 

1.7106 

26.0 

28.0 

246.41 

0.01695 

14.647 

14.664 

214.75 

947.7 

1162.4 

03624 

13422 

1.7046 

28.0 

30.0 

25034 

0.01698 

13.728 

13.745 

218.73 

945.0 

1163.7 

03680 

13310 

1.6990 

30.0 

32.0 

254.05 

0.01701 

12.923 

12.940 

222.50 

942.5 

1165.0 

03732 

13206 

1.6938 

32.0 

34.0 
36.0 
38.0 

257.58 
260.94 
264.16 

0.01704 
0.01707 
0.01710 

12209 
11.570 
10.998 

12226 
11.587 
11.015 

226.09 
22931 
232.79 

940.0 
937.7 
9353 

1166.1 
11672 
11683 

03783 
03830 
03876 

13107 
13014 
12925 

1.6890 
1.6844 
1.6800 

34.0 
36.0 
38.0 

40.0 
42.0 
44.0 
46.0 
48.0 

26724 
27021 
273.06 
275.81 
278.45 

0.01712 
0.01715 
0.01717 
0.01719 
0.01722 

10.480 
10.010 
9.582 
9.189 
8.829 

10.497 
10.027 
9399 
9207 
8.846 

235.93 
238.95 
241.86 
244.67 
24737 

9333 
9312 
9292 
9272 
925.4 

11692 
11702 
1171.1 
1171.9 
1172.7 

03919 
03961 
0.4000 
0.4039 
0.4076 

12840 
12759 
12682 
12608 
12537 

1.6759 
1.6720 
1.6683 
1.6647 
1.6613 

40.0 
42.0 
44.0 
46.0 
48.0 

60.0 
52.0 
54.0 
66.0 
68.0 

281.01 
283.49 
285.90 
28823 
290.50 

0.01724 
0.01726 
0.01728 
0.01730 
0.01732 

8.496 
8.189 
7.902 
7.636 
7388 

8.514 
8206 
7.919 
7.653 
7.405 

249.98 
25232 
254.99 
25738 
259.71 

923.5 
921.7 
920.0 
9183 
916.6 

11733 
11743 
1175.0 
1175.7 
1176.4 

0.4111 
0.4145 
0.4178 
0.4210 
0.4241 

12469 
12404 
1.2340 
12279 
12220 

1.6580 
1.6549 
1.6518 
1.6489 
1.6461 

50.0 
62.0 
54.0 
56.0 
58.0 

60.0 
62.0 
64.0 
66.0 
68.0 

292.71 
294.85 
296.94 
298.98 
300.98 

0.01735 
0.01737 
0.01739 
0.01741 
0.01743 

7.155 
6.937 
6.732 
6.539 
6357 

7.172 
6.955 
6.749 
6356 
6375 

261.98 
264.18 
26633 
268.43 
270.49 

915.0 
913.4 
911.9 
910.4 
908.9 

1177.0 
1177.6 
11782 
1178.8 
1179.4 

0.4271 
0.4300 
0.4329 
0.4356 
0.4384 

12162 
12107 
12053 
12001 
1.1950 

1.6434 
1.6407 
1.6382 
1.6357 
1.6333 

60.0 
62.0 
64.0 
66.0 
68.0 

70.0 
72.0 
74.0 
76.0 
78.0 

302.92 
304.82 
306.68 
30830 
31028 

0.01744 
0.01746 
0.01748 
0.01750 
0.01752 

6.186 
6.024 
5.870 
5.723 
5384 

6203 
6.041 
5.887 
5.741 
5.602 

272.49 
274.45 
27637 
27825 
280.09 

907.4 
906.0 
904.6 
9032 
901.9 

1179.9 
1180.5 
1181.0 
11813 
1182.0 

0.4410 
0.4435 
0.4460 
0.4485 
0.4509 

1.1900 
1.1852 
1.1805 
1.1759 
1.1714 

1.6310 
1.6287 
1.6265 
1.6244 
1.6223 

70.0 
72.0 
74.0 
76.0 
78.0 

80.0 
82.0 
84.0 
86.0 
88.0 

312.03 
313.74 
315.42 
317.06 
318.68 

0.01754 
0.01756 
0.01757 
0.01759 
0.01761 

5.452 
5325 
5204 
5.089 
4.979 

5.470 
5343 
5222 
5.107 
4.997 

281.90 
283.67 
285.42 
287.13 
288.80 

900.5 
8992 
897.9 
896.7 
895.4 

1182.4 
1182.9 
1183.4 
1183.8 
11842 

0.4532 
0.4555 
0.4578 
0.4599 
0.4621 

1.1670 
1.1627 
1.1586 
1.1545 
1.1505 

1.6202 
1.6182 
1.6163 
1.6144 
1.6126 

80.0 
82.0 
84.0 
86.0 
88.0 

90.0 
92.0 
94.0 
96.0 
98.0 

32027 
321.83 
32337 
324.88 
32637 

0.01763 
0.01764 
0.01766 
0.01768 
0.01769 

4.874 
4.773 
4.676 
4384 
4.494 

4.892 
4.791 
4.694 
4.602 
4.512 

290.45 
292.07 
293.67 
29525 
1296.80 

8942 
893.0 
891.8 
890.6 
889.4 

1184.6 
1185.0 
1185.4 
1185.8 
1186.2 

0.4642 
0.4663 
0.4683 
0.4703 
0.4723 

1.1465 
1.1427 
1.1389 
1.1352 
1.1316 

1.6107 
1.6090 
1.6072 
1.6055 
1.6038 

90.0 
92.0 
94.0 
96.0 
98.0 

28 


CHAPTER  1.   AIR,  WATER  AND  STEAM 


TABLES.    PROPERTIES  OF  SATURATED  STEAM:    PRESSURE  TABLE — (Continued) 


Specific  Volume 

Total  Heat 

Entropy 

Ab*.  Pr*»«. 
Lb./Sq.  In. 

BSfe 

Sat.                        Sat. 
Liquid   Evap.    Vapor 

Sat.                     Sat. 
Liquid   Evap.    Vapor 

Liquid      Evap.      Vapor 

Ab*.  Pr*M. 
Lb./Sq.  In. 

P 

t 

Vf           Vfg          Vg 

hf         hfg          hK 

Sf          Sfg            Sff 

P 

100.0 

327.83 

0.01771  4.408    4.426 

29833  888.2   1186.6 

0.4742    1.1280    1.6022 

100.0 

102.0 

329.27 

0.01773  4326    4344 

299.83   887.1   1186.9 

0.4761    1.1245    1.6006 

102.0 

104.0 

330.68 

0.01774  4.247    4.265 

30130  886.0   11873 

0.4779    1.1211    1.5990 

104.0 

106.0 

332.08 

0.01776  4.171    4.189 

302.76  884.9   1187.6 

0.4798    1.1177    1.5974 

106.0 

108.0 

333.44 

0.01777  4.097    4.115 

304.19  883.8   1188.0 

0.4816    1.1144    1.5959 

108.0 

110.0 

334.79 

0.01779  4.026    4.044 

305.61   882.7   11883 

0.4834    1.1111    1.5944 

110.0 

112.0 

336.12 

0.01780  3.958    3.976 

307.00   881.6   1188.6 

0.4851    1.1079    1.5930 

112.0 

114.0 

337.43 

0.01782   3.892    3.910 

30836  880.6  1188.9 

0.4868    1.1048    1.5915 

114.0 

116.0 

338.72 

0.01783  3.828    3.846 

309.71   879.5    1189.2 

0.4885    1.1017    1.5901 

116.0 

118.0 

340.01 

0.01785  3.766    3.784 

311.05   878.5   1189.5 

0.4901    1.0986    1.5887 

118.0 

120.0 

341.26 

0.01786  3.707    3.725 

31237  877.4  1189.8 

0.4918   1.0956   1.5874 

120.0 

122.0 

342.50 

0.01788  3.652    3.670 

313.67  876.4  1190.1 

0.4934    1.0926    1.586Q 

122.0 

124.0 

343.73 

0.01789  3.597    3.615 

314.96  875.4  1190.4 

0.4950    1.0897    1.5847 

124.0 

126.0 

344.94 

0.01791  3.542    3.560 

316.23  874.4   1190.6 

0.4965    1.0868    1.5834 

126.0 

128.0 

346.14 

0.01792  3.487    3.505 

317.49  873.4  1190.9 

0.4981    1.0840    1.5821 

128.0 

130.0 

347.31 

0.01794  3.433    3.451 

318.73  872.4  1191.2 

0.4996   1.0812    1.5808 

130.0 

132.0 

348.48 

0.01795  3383    3.401 

319.95   871.5   1191.4 

0.5011    1.0784    1.5796 

132.0 

134.0 

349.64 

0.01796  3335    3353 

321.17  870.5   1191.7 

0.5026   1.0757    1.5783 

134.0 

136.0 

350.78 

0.01798  3.288    3306 

32237   869.6   1191.9 

0.5041    1.0730    1.5771 

136.0 

138.0 

351.91 

0.01799  3.242    3.260 

323.56  868.6  1192.2 

0.5056   1,0703    1.5759 

138.0 

140.0 

353.03 

0.01801  3.198    3.216 

324.74  867.7  1192.4 

0.5070   1.0677   1.5747 

140.0 

142.0 

354.14 

0.01802  3.155    3.173 

325.91  .866.7   1192.6 

0.5084    1.0651    1.5735 

142.0 

144.0 

355.22 

O.Q1804  3.112    3.130 

327.06  865.8   1192.9 

0.5098   1.0625    1.5724 

144.0 

146.0 

35631 

0.01805  3.071    3.089 

328.20  864.9   1193.1 

0.5112    1.0600    1.5712 

146.0 

148.0 

35737 

0.01806  3.031    3.049 

32932  864.0  11933 

0.5126   1.0575    1.5701 

148.0 

150.0 

358.43 

0.01808  2.992    3.0'10 

330.44  863.1   1193.5 

0.5140   1.0550   1.5690 

150.0 

152.0 

359.47 

0.01809  2.954    2.972 

331.54  862.2   1193.7 

0.5153    1.0526    1.5679 

152.0 

154.0 

360.51 

0.01810  2.917    2.935 

332.64  8613   1193.9 

0.5166    1.0502    1.5668 

154.0 

156.0 

361.53 

0.01812  2.882    2.9QO 

333.72   860.4  1194.1 

0.5180    1.0478    1.5658 

156.0 

158.0 

362.54 

0.01813  2.846    2.864 

334.80  859.5   11943 

0.5193    1.0454   1.5647 

158.0 

160.0 

363.55 

0.01814  2.812    2.830 

335.86  858.7  1194.5 

0.5205    1.0431    1.5636 

160.0 

162.0 

364.54 

0.01816  2.779    2.797 

336.91  857.8  1194.7 

0.5218    1.0408    1.5626 

162.0 

164.0 

365.52 

0.01817  2.746    2.764 

337.95  857.0  1194.9 

0.5230    1.0385    1.5616 

164.0 

166.0 

366.50 

0.01818  2.715    2.733 

338.99  856.1   1195.1 

0.5243    1.0363    1.5606 

166.0 

168.0 

367.46 

0.01819  2.683    2.701 

340.01   855.2  11953 

0.5255   1.0340    1.5596 

168.0 

170.0 

368.42 

0.01821  2.653    2.671 

341.03   854.4  1195.4 

0.5268    1.0318    1.5586 

170.0 

172.0 

369.37 

0.01822  2.623    2.641 

342.04  853.6  1195.6 

0.5280    1.0296    1.5576 

172.0 

174.0 

370.31 

0.01823  2.594    2.612 

343.04  852.7  1195.8 

0.5292    1.0275    1.5566 

174.0 

176.0 

371.24 

0.01825  2.566    2.584 

344.03   851.9  1196.0 

0.5304    1.0253    1.5557 

176.0 

178.0 

372.16 

0.01826  2.538    2.556 

345.01  851.1  1196.1 

0.5315    1.0232    1.5548 

178.0 

180.0 

373.08 

0.01827  2.511    2.529 

345.99  8503  1196.3 

0.5327    1.0211    1.5538 

180.0 

182.0 

374.00 

0.01828  2.484    2.502 

346.97   849.5   1196.4 

0.5339    1.0190    1.5529 

182.0 

184.0 

374.90 

0.01829  2.458    2.476 

347.94  848.6  1196.6 

0.5350-  1.0169    1.5520 

184.0 

186.0 

375.78 

0.01831  2.433    2.451 

348.89  847.9  1196.8 

0.5362    1.0149    1.5511 

186.0 

188.0 

376.67 

0.01832  2.407    2.425 

349.83   847.1  1196.9 

0.5373    1.0129    1.5502 

188.0 

190.0 

377.55 

0.01833  2383    2.401 

350.77  8463  1197.0 

0.5384   1.0109    1.5493 

190.0 

192.0 

378.42 

0.01834  2359    2377 

351.70   845.5  1197.2 

0.5395    1.0089    1.5484 

192.0 

194.0 

379.27 

0.01835  2335    2353 

352.61   844.7  11973 

0.5406    1.0070    1.5475 

194.0 

196.0 

380.13 

0.01837  2312    2330 

353.53   844.0  1197.5 

0.5417   1.0050   1.5467 

196.0 

198.0 

380.97 

0:01838  2.289    2307 

354.43   843.2  1197.6 

0.5427    1.0031    1.5458 

198.0 

200.0 

381.82 

0.01839   2.267    2.285 

35533   842.4  1197.8 

0,5438   1.0012    1.5450 

200.0 

205.0 

383.89 

0.01842   2.213    2.231 

357.56  840.5  1198.1 

0.5465    0.9964    1.5429 

205.0 

210.0 

385.93 

0.01844  2.162    2.180 

359.76   838.6  1198.4 

0.5491    0.9918    1.5409 

210.0 

215.0 

387.93 

0.01847  2.113    2.131 

361.91  836.8  1198.7 

0.5516    0.9873    1.5389 

215.0 

220.0 

389.89 

0.01850  2.066    2.084 

364.02   835.0  1199.0 

0.5540   0.9829    1.5369 

220.0 

225.0 

391.81 

0.01853  2.0208  2.0393 

366.10  833.2  11993 

0.5565   0.9786    1.5350 

225.0 

230.0 

393.70 

0.01856  1.9778  1.9964 

368.14  831.4  1199.6 

0.5588    0.9743    1.5332 

230.0 

235.0 

395.56 

0.01859  1.9367  1.9553 

370.15   829.7  1199.8 

0.5612    0.9702    15313 

235.0 

240.0 

397.40 

0.01861   1.8970  1.9156 

372.13  827.9  1200.1 

0.5635    0.9661    1.5295 

240.0 

246.0 

399.20 

0.01864  1.8589  1.8775 

374.09  826.2  12003 

0,5658   0.9620    1.5278 

245.0 

HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 

TABLE  8.    PROPERTIES  OF  SATURATED  STEAM:    PRESSURE  TABLE—  (Concluded) 

Specific  Volume 

Total  Heat 

Entropy 

AW.  Pr*«. 

T«rop. 

Sat.                         Sat. 

Sat.                    Sat. 

Sat.                        Sat. 

Ab«.  Pratt. 

Lb.,Sq.  In. 

D*t>  F. 

Liquid     Evap.     Vapor 

Liquid    Evap.    Vapor 

Liquid      Evap.      Vapor 

Lb./Sq.  In. 

P 

t 

Vf           Vf*          Vg 

hf         hfg          hg 

Sf          Sfg           Sg 

P 

260.0 

400.97 

0.01867  1.8223   1.8410 

376.02  824.5   12003 

0.5680  0.9581    1.5261 

260.0 

260.0 

404.43 

0.01872  1.7536  1.7723 

379.78  821.2   1201.0 

0.5723  0.9504   1.5227 

260.0 

270.0 

407.79 

0.01877   1.6895    1.7083 

383.44   818.0   1201.4 

0.5765   0.9430   13194 

270.0 

280.0 

411.06 

0.01882   1.6302   1.6490 

387.02  814.7   1201.8 

0.5805  0.9357   1.5163 

280.0 

290.0 

41454 

0.01887   1.5745   13934 

390.50  811.6  1202.1 

0.5845  0.9287    13132 

290.0 

300.0 

41733 

0.01892   1.5225   1.5414 

393.90  808.5   1202.4 

03883   0.9220    13102 

300.0 

320.0 

42359 

0.01901   1.4279   1.4469 

400.47  8023   1203.0 

0.5957  0.9089   1.5046 

320.0 

340.0 

428.96 

0.01910  13439   13630 

406.75  796.6  1203.4 

0.6027  0.8965    1.4992 

340.0 

360.0 

434.39 

0.01918   15689   15881 

412.80  790.9   1203.7 

0.6094  0.8846   1.4940 

360.0 

380.0 

439.59 

0.01927  15015   15208 

418.61   7853   1203.9 

0.6157  0.8733   1.4.891 

380.0 

400.0 

444.58 

0.0194     1.1407   1.1601 

4245     779.8  1204.1 

0.6218  0.8625   1.4843 

400.0 

420.0 

44938 

0.0194     1.0853   1.1047 

429.6     774.5   1204.1 

0.6277  0.8520    1.4798 

420.0 

440.0 

454.01 

0.0195     1.0345   1.0540 

434.8     7693   1204.1 

0.6334  0.8420   1.4753 

440.0 

460.0 

458.48 

0.0196     0.9881   1.0077 

439.9     764.1   1204.0 

0.6388   0.8322    1.4711 

460.0 

480.0 

462.80 

0.0197     0.9456  0.9633 

444.9     759.0   1203.9 

0.6441   0.8228    1.4670 

480.0 

600.0 

466.99 

0.0198     0.9063   0.9261 

449.7     754.0  1203.7 

0.6493  0.8137    1.4630 

600.0 

620.0 

471.05 

0.0198     0.8701   0.8899 

454.4     749.0  1203.5 

0.6543  0.8048    1.4591 

520.0 

640.0 

474.99 

0.0199     0.8363  0.8562 

459.0     744.1   12035 

0.6592  0.7962    1.4554 

640.0 

660.0 

478.82 

0.0200     0.8047  0.8247 

463.6     7393   1202.9 

0.6639  0.7878    1.4517 

660.0 

680.0 

482.55 

0.0201     0.7751   0.7952 

468.0     734.5   1202.5 

0.6686  0.7796   1.4482 

680.0 

600.0 

486.17 

0.0202     0.7475   0.7677 

4723     729.8   1202.1 

0.6731  0.7716   1.4447 

600.0 

620.0 

489.71 

0.0202     0.7217   0.7419 

476.6     725.1   1201.7 

0.6775  0.7638   1.4413 

620.0 

640.0 

493.16 

0.0203     0.6972  0.7175 

480.8     7203   12015 

0.6818  0.7562   1.4380 

640.0 

660.0 

496.53 

0.0204     0.6744  0.6948 

484.9     715.9   1200.8 

0,6861  0.7487   1.4348 

660.0 

680.0 

49932 

0.0205     0.6527  0.6732 

488.9     7113   12005 

0.6902  0.7414   1.4316 

680.0 

700.0 

503.04 

0.6206     0.6321   0.6527 

492.9     706.8   1199.7 

0.6943  0.7342   1.4285 

700.0 

720.0 

506.19 

0.0206     0.6128  0.6334 

496.8     702.4   11995 

0.6983  0.7272   1.4255 

720.0 

740.0 

509.28 

0.0207     03944  0.6151 

500.6     697.9   1198.6 

0.7022  0.7203   1.4225 

740.0 

760.0 

51230 

0.0208     0.5769  03977 

504.4     693.5   1198.0 

0.7060  0.7136   1.4196 

760.0 

780.0 

51557 

0.0209     0.5602  03811 

5085     689.2   1197.4 

0.7098  0.7069   1.4167 

780.0 

800.0 

518.18 

0.0209     0.5444  03653 

511.8     684.9   1196.7 

0.7135  0.7004   1.4139 

800.0 

820.0 

521.03 

0.0210     03293  03503 

5153     680.6   1196.0 

0.7171  0.6940   1.4111 

S20.0 

840.0 
860.0 

523.83 
526.58 

0.0211     03149  0.5360 
0.0212     03013   03225 

519.0     676.4  1195.4 
522.6     672.1   1194.7 

0.7207  0.6877   1.4084 
0.7242  0.6815   1.4057 

840.0 
860.0 

880.0 

52959 

0.0213     0.4881   03094 

526.0     667.9   1194.0 

0.7277  0.6754  1.4031 

880.0 

900.0 
920.0 
940.0 
960.0 
980.0 

531.95 
534.56 
537.13 
539.66 
542.14 

0.0213     0.4756  0.4969 
0.0214     0.4635   0.4849 
0.0215     0.4520  0.4735 
0.0216     0.4409  0.4625 
0.0217     0.4303   0.4520 

5293     663.8   11933 
532.9     659.7  1192.6 
5365     655.6   1191.8 
539.6     651.5   1191.1 
542.8     647.5   11903 

0.7311  0.6694   1.4005 
0.7344  0.6635   1.3980 
0.7377  0.6577   1.3954 
0.7410  0.6520   1.3930 
0.7442  0.6464   1.3905 

900.0 
920.0 
940.0 
960.0 
980.0 

1000.0 
1060.0 
1100.0 
1160.0 
1200.0 

544.58 
55033 
55658 
561.81 
567.14 

0.0217     0.4202   0.4419 
0.0219     03960  0,4179 
0.0222     03738  03960 
0.0224     03540  03764 
0.0226     03356  03582 

546.0     643.5   1189.6 
554.0     633.6  1187.6 
561.7     623.9  1185.6 
5695     6143  1183.5 
576.5     604.9   1181.4 

0.7473   0.6408   13881 
0.7550  0.6273   13822 
0.7624  0.6141   1.3765 
0.7695  0.6014  13709 
0.7764  03891   13656 

1000.0 
1060.0 
1100.0 
1160.0 
1200.0 

1260.0 
1300.0 
1360.0 
1400.0 
1460.0 

57230 
57732 
58251 
586.96 
591.58 

0.0228     03187  03415 
0.0230     03029   03259 
0.0232     05884  03116 
0.0235     05748  05983 
0.0237     05621  05858 

583.6     595.6  1179.2 
590.6     5863   1177.0 
597.5     5775  1174.7 
6043     568.1   1172.4 
•611.0     559.1   1170.0 

0.7831  03772   13603 
0.7897  03654  13552 
0.7962  03540  13501 
0.8024  03428  1.3452 
0.8086  0.5318  13404 

1260.0 
1300.0 
1360.0 
1400.0 
1460.0 

1500.0 
1600.0 
1700.0 
1800.0 
1900.0 

5964)8 
604.74 
612.98 
620.86 
62839 

0.0239     05502  05741 
0.0244     05284  05528 
0.0249     05089  0.2338 
0.0254     0.1913  05167 
0.0260     0.1754  05014 

617.5     5505  1167.6 
6305     532.6  1162.7 
6423     515.0  1157.5 
654.7     4975   115L8 
666.8     478.9  1145.7 

0.8146  0:5212  13357 
0.8262  0.5003   13265 
0.8373  0.4801   13174 
0.8482  0.4601   13083 
0.8589  0.4402  15990 

1600.0 
1600.0 
1700.0 
1800.0 
1900.0 

ooooo 

635.6 
6495 
661.9 
673.8 
684.9 

0.0265     0.1610  0.1875 
0.0277     0.1346  0.1623 
0.0292     0.1112  0.1404 
0.0310     0.0895  0.1205 
0.0333     0.0688  0.1021 

679.0     460.0  1139.0 
703.7     420.0  1123.8 
729.4     376.4  1105.8 
756.7     327.8  10843 
786.7     2723  1058.9 

0.8696  0.4200  15896 
0.8912  03788  15700 
0.9133  03356  15488 
0.9364  05892   15257 
0.9618  05379  1.1996 

2000.0 
2200.0 
2400.0 
2600.0 
2800.0 

3000.0 
3200.0 
3226.0 

6955 
704.9 
706.1 

0.0367     0,0477  0.0844 
O.C459     0.0142  0.0601 
0.0522         0      0.0522 

823.1     202.5  1025.6 
887.0       75.9     962.9 
925.0       0        925.0 

0.9922  0.1754  1.1676 
1.0461  0.0651   1.1112 
1.0785      0       1.0785 

3000.0 
3200.0 
3226.0 

-    30 


CHAPTER  1.   AIR,  WATER  AND  STEAM 


responding  change  in  the  latent  heat  of  evaporation.    These  values  are 
given  in  Table  8. 

Specific  Heat.  The  specific  heat  of  water,  or  the  amount  of  heat  (Btu) 
required  to  raise  the  temperature  of  one  pound  of  water  one  degree  Fahren- 
heit, varies  with  the  temperature,  but  it  is  commonly  assumed  to  be 
unity  at  all  temperatures.  Steam  tables  are  based  on  exact  values, 
however.  The  specific  heat  of  ice  at  32  F  is  0.492  Btu  per  pound.  The 
amount  of  heat  required  to  raise  one  pound  of  water  at  32  F  through  a 
known  temperature  interval  depends  on  the  average  specific  heat  for  the 
temperature  range. 

Sensible  and  Latent  Heat.  The  heat  necessary  to  raise  the  temperature 
of  one  pound  of  water  from  32  F  to  the  boiling  point  is  known  as  the  heat 
of  the  liquid  or  sensible  heat.  When  more  heat  is  added,  the  water  begins 
to  evaporate  and  expand  at  constant  temperature  until  the  water  is 
entirely  changed  into  steam.  The  heat  thus  added  is  known  as  the  latent 
heat  of  evaporation. 

PROPERTIES  OF  STEAM 

Steam  is  water  vapor  which  exists  in  the  vaporous  condition  because 
sufficient  heat  has  been  added  to  the  water  to  supply  the  latent  heat  of 
evaporation  and  change  the  liquid  into  vapor.  This  change  in  state  takes 
place  at  a  definite  and  constant  temperature  which  is  determined  solely 
by  the  pressure  of  the  steam.  The  volume  of  a  pound  of  steam  is  the 
specific  volume  which  decreases  as  the  pressure  increases.  The  reciprocal 
of  this,  or  the  weight  of  steam  per  cubic  foot,  is  the  density.  (See  Table  8.) 

Steam  which  is  in  contact  with  the  water  from  which  it  was  generated  is 
known  as  saturated  steam.  If  it  contains  no  actual  water  in  the  form  of 
mist  or  priming,  it  is  called  dry  saturated^  steam.  If  this  be  heated  and  the 
pressure  maintained  the  same  as  when  it  was  vaporized,  its  temperature 
will  increase  and  it  will  become  super-heated,  that  is,  its  temperature  will 
be  higher  than  that  of  saturated  steam  at  the  same  pressure. 

REFERENCES 

Temperature  of  Evaporation,  by  W.  H.  Carrier  (A.S.H.V.E.  TRANSACTIONS,  Vol.  24, 
1918,  p.  25). 

The  Evaporation  of  a  Liquid  into  a  Gas,  by  W.  K.  Lewis  (A.S.M.E.  Transactions, 
Vol.  44,  1922). 

The  Evaporation  of  a  Liquid  into  a  Gas — a  Correction,  by  W.  K.  Lewis  (Mechanical 
Engineering,  September,  1933). 

Temperature  of  Evaporation  of  Water  into  Air,  by  W.  H.  Carrier  and  D.  C.  Lindsay 
(A.S.M.E.  Transactions,  Vol.  46,  1924). 

A  New  Psychrometric  or  Humidity  Chart,  by  C.  A.  Bulkeley  (A.S.H.V.E.  TRANS- 
ACTIONS, Vol.  32,  1926,  p.  163). 

A  Review  of  Psychrometric  Charts,  by  C.  O.  Mackey  (Heating  and  Ventilating, 
June,  July,  1931). 

Air  Conditioning  Applied  to  Cold  Storage  and  a  New  Psychrometric  Chart,  by  C,  A. 
Bulkeley  (Refrigerating  Engineering,  February,  1932). 

The  Psychrometric  Chart,  by  E.  V.  Hill  (Aerologist,  April,  May,  June,  1932). 

Air  Conditioning  Theory,  by  John  A.  Goff  (Refrigerating  Engineering,  January,  1933). 

Mixtures  of  Air  and  Water  Vapor,  by  C.  A.  Bulkeley  (Refrigerating  Engineering, 
January,  1933). 

31 


HEATING   VENTILATING   AIR  CONDITIONING  GUIDE  1938 

Basic  Theory  of  Air  Conditioning,  by  Lawrence  Washington  (Western  Conference  on 
Air  Conditioning,  San  Francisco,  Calif.,  February  9-10,  1933). 

The  Theory  of  the  Psychrometer,  by  J.  H.  Arnold  (Physics,  July,  September,  1933). 

Heat  Transmission  in  Cooling  Air  with  Extended  Surfaces,  by  W.  L.  Knaus  (Refrigera- 
ting Engineering,  Januar>T,  February,  1935). 

A  New  Psychrometric  Chart,  by  F.  0.  Urban  (Refrigerating  Engineering,  November 
1935). 

Psychrometric  Charts,  by  Donald  B.  Brooks  (U.  S.  Bureau  of  Standards  Miscellaneous 
Publication  No.  143). 

The  Deviation  of  the  Actual  Wet-Bulb  Temperature  from  the  Temperature  of 
Adiabatic  Saturation,  by  David  Dropkin  (Cornell  University  Engr.  Exp.  Station  Bui. 
No.  23,  July,  1936). 


PROBLEMS  IN  PRACTICE 

1  •  Given  air  at  70  F  dry-bulb  and  50  per  cent  relative  humidity  with  a  baro- 
metric pressure  of  29.00  in.  Hg,  find  the  weight  of  vapor  per  pound  of  dry  air. 

Pressure  of  saturated  vapor  -  et  =  0.7387  in.  Hg  (Table  6). 
From  Equation  5a, 

0.5  X  0.7387  \ 

-  (0.5)  X  (0.7387)7 

W  =  0.008024  lb  of  vapor  per  pound  of  dry  air  at  70  F  dry-bulb  and  50  per  cent 
relative  humidity. 

Approximate  Method: 

Weight  of  saturated  vapor  per  pound  of  dry  air  =  Wt  =  0.01574  lb  (Table  6).  0.01574 
X  0.5  =  0.00787  lb  of  vapor  per  pound  of  dry  air  at  70  F  dry-bulb  and  50  per  cent  relative 
humidity. 

2  •  Given  ah-  with  a  dry-bulb  temperature  of  80  F,  relative  humidity  of  55  per 
cent,  and  a  barometric  pressure  of  28.85  in.  Hg,  calculate  the  weight  of  a  cubic 
foot  of  mixture. 

Pressure  of  saturated  vapor  at  80  F  =  et  =  1.0316  in.  Hg  (Table  6). 
Pressure  of  the  vapor  in  the  mixture  -  1.0316  X  0.55  =  0.5676  in.  Hg. 
Pressure  of  the  dry  air  in  the  mixture  =  28.85  -  0.5676  =  28.282  in.  Hg. 


__        28.282 

~  0.753  X  540  ™  °-06955  lb  =  weight  of  dry  air  in  1  cu  ft  of  the  mixture. 

Likewise  from  Equation  4a, 


^  =    1.21  X  540    =  0-W0868  lb  -  weight  of  vapor  per  cubic  foot  at  55  per  cent 
relative  humidity. 
Weight  of  1  cu  ft  of  the  mixture  =  0.06955  +  0.000868  =  0.070418  lb.  ' 

3  •  Given  air  with  a  dry-bulb  temperature  of  75  F,  a  relative  humidity  of  60  per 
cent,  and  a  barometric  pressure  of  28.80  in.  Hg,  calculate  the  volume  of  1  lb  of 

ine  mixture. 

Pressure  of  saturated  vapor  at  75  F  =  et  ===  0.8745  in.  Hg. 
Pressure  of  vapor  in  the  mixture  =  0.8745  X  0.6  ~  0.525  in.  Hg. 
Pressure  of  dry  air  in  the  mixture  «  28.80  -  0.525  -  28.275  in.  Hg. 

32 


CHAPTER  1.   AIR,  WATER  AND  STEAM 


^     =  ______  28.275  _  =  0.07018  Ib  =  weight  of  dry  air  in  1  cu  ft  of  the  mixture. 

0.753  X  535 

From  Equation  4a, 

j     _         Q*525  _  =  0  000811  Ib  =  weight  of  vapor  per  cubic  foot  at  55  per  cent 

**  "    1.21  X  535 
relative  humidity. 
Weight  of  1  cu  ft  of  the  mixture  =  0.07018  -f  0.000811  =  0.070991  Ib. 

Volume  of  1  Ib  of  the  mixture  =  -Q^ggf  =  14-08  cu  ft- 


4  ®  It  is  desired  to  maintain  a  temperature  of  80  F  and  a  relative  humidity  of 
^  per  cent  in  a  factory  where  the  equipment  gives  off  6,000  Btu  per  hour  If 
th«f  entering  ah-  is  at  70  F  with  an  average  barometric  pressure  of  29.92  m.  Hg, 
determSe  the  relative  humidity,  and  the  pounds  of  an:  required  pex  -hour  *f 
there  is  no  heat  interchange  between  the  walls,  windows,  or  floors  of  the 
building. 

Pressure  of  saturated  vapor  at  80  F  =  1.0316  in.  Hg  (Table  6). 
Pressure  of  vapor  in  the  mixture  -  1.0316  X  0.5  =  0.5158  in.  Hg. 

IF  =  0-622  (  ^S^  )=  0.01091  Ib. 

Pressure  of  saturated  vapor  at  70  F  «  0,7387  in.  Hg. 

With  the  same  specific  humidity 

/          0.7387  X 
0.01091  -  0.622  (29.92  „ 


$  =  69.8  per  cent  relative  humidity  at  70  F.    , 

h  =  0  24  X  80  +  0.01091  [1059.2  +  (0.45  X  80)]  =  31.15  Btu  per  pound,  the  heat  con- 
tent of  the  mixture  at  80  F  and  50  per  cent  relative  humidity. 

h  =  0  24  X  70  +  0.01091  [1059.2  +  (0.45  X  70)]  =  28.70  Btu  per  pound,  the  heat  con- 
tent of  the  mixture  at  70  F  and  the  same  specific  humidity. 
31.15  —  28.70  =  2.45  Btu  to  be  removed  per  pound  of  air. 
6000  Btu  =  heat  given  off  by  equipment  per  hour. 


6000 
2.45 


=  2449  Ib  of  air  required  per  hour. 


. 

remains  constant,  what  will  be  the  new  pressure,  P2,  in  in.  Hg? 


PV  =  w£(* 

R  (for  air)  =  53.34. 

W  =  1  Ib. 

P  =  absolute  pressure,  pounds  per  square  foot. 
1  X  53.34  X  (78  +  460) 

/    "      29.92  X  0.491  X  144 

V  =  13.57  cu  ft  =  volume  of  1  Ib. 

P*  _  T*      p    -  T*P* 

Pi  -  3\;       2          Ti 

v    .  (96  +  460)  (29.92  X  0.491  X  144)    =  3Q  M  .^  Hg 

^2  -          (7g  +  460)  (0.491  X  144) 


including  the  heat  content  of  the  liquid  above  32  F. 

33 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

From  Equation  12, 

h  =  0.24  ft  -  0)  +  Wh+ 
where 

hs  «  1059.2  +  0.45*'  (Empirical  equation  derived  from  Keenan's  Steam  Tables). 

/'  =  75  F. 
W  «  0.01873  Ib  of  water  vapor  (Table  6). 

h  -  0.24  (75  -  0)  -f  0.01873  [1059.2  +  (0.45  X  75)]. 

h  =  38.46  Btu  per  pound  of  dry  air. 

7  •  A  building  requires  50,000  cu  ft  of  air  per  hour  to  be  raised  from  — 10  F 
dry-bulb  and  75  per  cent  relative  humidity  to  72  F  dry-bulb  and  30  per  cent 
relative  humidity.    Determine  the  amount  of  heat  and  the  weight  of  water 
which  it  is  necessary  to  supply  per  hour  if  the  temperature  of  the  supply  water 
is  50  F  and  the  barometric  pressure  is  28.75  in.  Hg. 

Assume  air  volume  to  be  dry  air  at  70  F. 

Weight  of  air  «  0.075  X  50,000  -  3750  Ib  per  hour. 

From  Table  6, 

Pressure  of  vapor  in  the  mixture,  outside  air  =  0.75  X  0.0221  =  0.0166  in.  Hg. 

Specific  humidity,  outside  air  -  0.622  (  2g  75° '- cfoiee  )  "  °-0003589  Ib> 

From  Table  6, 

Pressure  of  vapor  in  the  mixture,  inside  air  =  0.30  X  0.7906  =  0.2372  in.  Hg. 

Specific  humidity,  inside  air  =  0.622  (2g  75°^ 3Q  237is)  =  ao05174  lb- 
Water  to  be  added  =  3750  (0.005174  -  0.0003589  )  =  18.06  lb  per  hour. 

Heat  content,  inside  air  =  0.24  X  72  -f  0.005174  [1059.2  +  (0.45  X  72)]  -  22.925  Btu 
per  pound. 

Heat  content,  outside  air  «  0.24  X  (-10)  -f-  0.0003589  [1059.2  -f  (0.45  X  -10)]  = 
-2.021  Btu  per  pound. 

Btu  added  incident  to  the  water  per  pound  of  dry  air. 

(0.005174  -  0.0003589)  (50  -  32)  =  0.0867  Btu  per  pound. 

Heat  requirement  per  hour  =  [22.925  -  (-2.021  +  0.0867)]  X  3750  =  93,221  Btu. 

8  •  Determine  the  amount  of  heat  and  water  that  must  be  extracted  to  cool 
3750  lb  of  air  (weighed  dry)  from  95  F  and  60  per  cent  relative  humidity  to  50  F 
and  100  per  cent  relative  humidity  with  a  barometric  pressure  of  28.75  in.  Hg. 

Pressure  of  vapor  in  the  mixture,  outside  air  =  0.6  X  1.659  =  0.995  in.  Hg. 

Specific  humidity,  outside  air  =  0.622  [  no  >.,       ^  Mtf}  =  0.0223  lb. 

\28.7o  —  0.995  / 
Specific  humidity,  inside  air  -  0.007626  lb. 

Weight  of  water  to  be  extracted  per  hour  =  (0.0223  -  0.007626)  X  3750  =  55.03  lb. 

Heat  content,  outside  air  =  0.24  X  95  +  0.0223  [1059.2  -f  (0.45  X  95)]  -  47.37  Btu 
per  pound. 

Heat  content,  inside  air  -  0.24  X  50  -h  0.00764  [1059.2  +  (0.45  X  50)]  =  20.26  Btu 
per  pound. 

Heat  to  be  extracted  =  (47.37  -  20.26)  X  3750  =  101,662  Btu. 


34 


Chapter  2 

REFRIGERANTS  AND  AIR  DRYING  AGENTS 


Properties  o£  Refrigerant  Substances,  Selection  Fact£r^olid 

Adsorbents,  Liquid  Absorbents,  Nature  o£  Processes,  Tempera- 

ture Pressure  Concentration  Relations 


BOTH  cooling  and  dehumidification  of  air  are  usually  desirable  at 
certain  times.  Cooling  may  be  regarded  as  the  extraction  of  sensible 
heat  while  dehumidification  necessitates  the  removal  of  patent  heat.  By 
a  suitable  selection  and  combination  of  methods  M*^™***^^ 
processes  may  be  accomplished  simultaneously  or  they  ^^6  secured 
independent  of  each  other  and  at  different  times  as  desired  On  occasion 
the  desired  result  can  be  secured  by  extracting  sensible  heat  only  while 
in  other  cases  drying  alone  will  produce  the  end  conditions  sought. 
SuiSble  substances  must  be  available  for  use  in  every  particular  case 
Generally,  when  both  cooling  and  dehumidification  are  fO"^  current 
oractice  makes  use  of  artificially  produced  refrigeration  in  some  forrn^ 

air  conditioning  work.  Little  mention  is  made  here  °f  methods,  i  y  stems 
or  equipment  whereby  these  substances  may  be  applied,  which  mtor 
mation  may  be  found  in  Chapter  24. 

REFRIGERANTS 

Since  air  cooling  and  dehumidification  are  frequently  Accomplished  by 
evaoorating  a  liquid  under  circumstances  which  will  permit  the  neat 
necSSrv  to  be  Sracted  from  the  air,  the  refrigerants  are  substances 

Considerations  including  availability,  cost,  safety  chemical  stability  and 
adaptability  to  the  type  of  refrigerating  system  to  be  used. 

In  this  chapter  detailed  consideration  is  limited  to  six  substances  viz 
ammonia,  carbon  dioxide,  dichlorodiftuoromethane  (P12),  methyl 


35 


HEATING  VENTILATING  AIR  CONDITIONING   GUIDE  1938 


TABLE  1.    PROPERTIES  OF  AMMONIA 


HEAT  CONTENT  AND  ENTROPY  TA.KEN  FROM  —40  F 


T^p<     Ln  PER                                         Heat  Content 
t         So  Is. 

Entropy 

100  F  Superhea 

200  F  Superheat 

i    Liquid     ,     Vapor     ,  Liquid 

Vapor 

Liqui 

Vapo 

Ht.C 

Entro 

Ht.  C 

Entropy 

0    ,  30.42  0.0241 

?    9.116 

42 

611.  i 

30.097 

1.335 

666 

1.443 

720 

1.5317 

2       31.92:0.0242 

4    8.714 

45 

612.' 

tO.  102 

1.331 

667 

1.440( 

721 

1.5277 

4    j  33  .47,;  0.02430    8.333 

47 

613.  ( 

)0.106 

1.327 

668 

1.436 

722 

1.5236 

5       34.  27*0.02432    8.150  \    48 

613.; 

50.109 

1.325 

668 

1.434 

722 

1.5216 

6       35.09  0.02435    7.971  !    49 

613.  < 

50.111 

1.323 

669 

1.432 

723 

1.5196 

8    ,  36.77  0.02440    7.629 

51 

614.; 

JO.  116 

1.319 

670 

1.428 

724 

1.5155 

10       38.51  0.0244< 

S    7.304 

53 

614.  < 

J0.120 

1.315 

670. 

1.424 

725 

1.5115 

12       40.3l!  0.0245] 

I    6.996 

56. 

615.* 

J0.125 

1.311 

671. 

1.420 

725 

1.5077 

14       42.180.0245' 

"    6,703 

58. 

616.1 

0.130C 

1.308 

672. 

1.416 

726. 

1.5039 

16       44.12  0.02462    6.425 

60. 

616.  e 

>  0.134 

1.304 

673. 

1.413 

727. 

1.5001 

18 

46.13  0.02465 

J    6.161 

62. 

617.2 

10.139 

1.300 

674. 

1.409 

728. 

1  .4963 

20 

48.2110.02474    5.910 

64. 

617. 

0.143 

1.296 

675. 

1.405 

729. 

1.4925 

22 

50.36  0.0247S 

>    5.671 

66. 

618. 

0.148 

1.293 

675. 

1.402 

730. 

1  .4889 

24 

52.59  0.0248 

5.443 

69. 

618. 

0.152 

1.289 

676. 

1.398 

731. 

1.4853 

26 

54.90,  0.0249 

5.227 

71. 

619. 

0.157 

1.286 

677. 

1.395 

732. 

1  .4816 

28 

57.28  0.0249 

5.021 

73. 

619. 

0.161 

1.282 

678. 

1.391 

733. 

1  .4780 

30 

59.74i  0.0250 

4.825 

75. 

620. 

0.166 

1.279 

678. 

1.387 

734. 

1.4744 

32 

62.291  0.0250 

4.637 

77. 

621. 

0.170 

1.275 

679. 

1.384 

735. 

1.4710 

34 

64.91 

0.0251 

4.459 

80. 

621. 

0.175 

1.272 

680. 

1.381 

736. 

1.4676 

36 

67.63 

1  0.0252 

4.289 

82. 

622. 

0.179 

1.268 

681. 

1.377 

736. 

1.4643 

38 

70.4310.0252 

4.126 

84. 

622. 

0.184 

1.2652 

681. 

1.374 

737. 

1.4609 

39       71.8710.0253 

4.048 

85. 

622. 

0.186 

1.2635 

682. 

1.372 

738. 

1.4592 

40    j  73.32  0.0253 

3.971 

86. 

623. 

0.1885 

1.2618 

682. 

1.3712 

738. 

1.4575 

41 

74.  80j  0.0253 

3.897 

87. 

623. 

0.1908 

1.2602 

683. 

1.3696 

739.0 

1.4559 

42 

76.31 

0.02539 

3.823 

89.0 

623.4 

0.1930 

1.2585 

683.4 

1.3680 

739.5 

1.4542 

44 

79.38 

0.02545 

3.682 

91.2 

623.9 

0.1974 

.2552 

684.2 

1.3648 

740  4 

.4510 

46 

82.55 

0.0255 

3.547 

93.5 

624.4 

0.2018 

.2519 

684.9 

.3616 

741.3 

.4477 

48 

85.82 

0.02558 

3.418 

95.7 

624.8 

0.2062 

.2486 

685.6 

.3584 

742  2 

.4445 

50 

89.19 

0.02564 

3.294 

97.9 

625.2 

0.2105 

.2453 

686.4 

.3552 

743.1 

.4412 

52 

92.66 

0.02571 

3.176 

100.2 

625.7 

0.2149 

.2421 

687.1 

.3521 

744.0 

!4382 

54 

96.23 

0.02577 

3.063 

102.4 

626.1 

0.2192 

.2389 

687.8 

.3491 

744.8 

.4351 

56 

99.91 

0.02584 

2.954 

104.7 

626.5 

0.2236 

.2357 

688.5 

.3460 

745.7 

.4321 

58 

103.7 

0.02590 

2.851 

106.9 

626.9 

0.2279 

.2325 

689.2 

.3430 

746  5 

4290 

60 
62 

107.6 
111.6 

0.02597 
0.02604 

2.751 
2.656 

109.2 
111.5 

627.3 
627.7 

0.2322 
0.2365 

.2294 
.2262 

689.9 
690.6 

.3399 
.3370 

747.4 
748.2 

.'4260 
4231 

66 
68 
70 
72 
74 
76 
78 
80 
82 
84 
86 
88 
90 
92 
94 
96 
98 
100 
102     ; 

115.7 
120.0 
124.3 
128.8 
133.4 
138.1 
143.0 
147.9 
153.0 
158.3 
163.7 
169.2 
174.8 
180.6 
186.6 
192.7 
198.9 
205.3 
211.9 
218.6 

0.02611 
0.02618 
0.02625 
0.02632 
0.02639 
0.02646 
0.02653 
0.02661 
0.02668 
0.02675 
0.02684 
0.02691 
0.02699 
0.02707 
0.02715 
0.02723 
0.02731 
0.02739 
0.02747 
0.02756 

2.565 
2.477 
2.393 
2.312 
2.235 
2.161 
2.089 
2.021 
1.955 
1.892 
1.831 
1.772 
1.716 
1.661 
1.609 
1.559 
1.510 
1,464 
1.419 
1.375 

113.7 
116.0 
118.3 
120.5 
122.8 
125.1 
127.4 
129.7 
132.0 
134.3 
136.6 
138.9 
141.2 
143.5 
145.8 
148.2 
150.5 
152.9 
155.2 
157.6 

628.0 
628.4 
628.8 
629.1 
629.4 
629.8 
630.1 
630.4 
630.7 
631.0 
631.3 
631.5 
631.8 
632.0 
632.2 
632.5 
632.6 
632.9 
633.0 
633.2 

0.2408 
.2451 
.2494 
.2537 
.2579 
.2622 
.2664 
.2706 
.2749 
.2791 
.2833 
.2875 
.2917 
.2958 
.3000 
.3041 
.3083 
.3125 
.3166 
.3207 

.2231 
.2201 
.2170 
.2140 
.2110 
2080 
2050 
2020 
1991 
1962 
1933 
1904 
1875 
1846 
1818 
1789 
1761 
1733 
1705 
1677 

691.3 
691.9 
692.6 
693.3 
694.0 
694.6 
695.3 
695.9 
696.6 
697.2 
697.8 
698.5 
99.1 
99.7 
00.3 
00.9 
01.5 
02.1 
02.7 
03.3 

.3341 
.3312 
.3283 
.3254 
.3226 
.3199 
.3171 
.3144 
.3116 
.3089 
3063 
3040 
3010 
2983 
2957 
2932 
2906 
2881 
2855 
2830 

749.1 
749.9 
750.8 
751.6 
752.4 
753.3 
754.1 
755.0 
755.8 
756.6 
757.4 
758.3 
759.1 
759.9 
760.7 
61.5 
62.2 
63.0 
63.8 
64.6 

.4202 
.4172 
.4143 
.4114 
.4086 
.4059 
.4031 
.4004 
3976 
3949 
3923 
3896 
3870 
3843 
3818 
3793 
3768 
3743 
3718 
3693 

36 


CHAPTER  2.  REFRIGERANTS  AND  AIR  DRYING  AGENTS 


TABLE  1.    PROPERTIES  OF  AMMONIA— (Continued) 


HEAT  CONTENT  AND  ENTROPY  TAKEN  FROM  -40  F 

o.m 

ABB 

.» 

oAT. 

TEMP. 

F 

PRESS. 
LB  PER 

SQlN. 

V  OLUME 

Heat  Content 

Entropy 

100  F  Superheat 

200  F  Superheat 

Liquid 

Vapor 

Liquid 

Vapor 

Liquid 

Vapor 

Ht.  Ct. 

Entropy 

Ht.  Ct. 

Entropy 

104 

225.4 

0.0276* 

1.334 

159.9 

633.4 

0.3248 

1.1649 

703.8 

1.2805 

765.3 

1.3668 

106 

232.5 

0.02773 

1.293 

162.3 

633.5 

0.3289 

1.1621 

701.3 

1.2780 

766.1 

1.3643 

108 

239.7 

0.02782 

1.254 

164.6 

633.6 

0.3330 

1.1593 

705.0 

1.2755 

766.9 

1.3619 

110 

247.0 

0.02790 

1.217 

167.0 

633.7 

0.3372 

1.1566 

705.5 

.2731 

767.6 

1.3596 

112 

254.5 

0.02799 

1.180 

169.4 

633.8 

0.3413 

1.1538 

706.1 

.2708 

768.3 

1.3573 

114 

262.2 

0.02808 

1.145 

171.8 

633.9 

0.3453 

1.1510 

706.6 

.2684 

769.1 

1.3550 

116 

270.1 

0.02817 

1.112 

174.2 

634.0 

0.3495 

1.1483 

707.2 

.2661 

769.8 

1.3527 

118 

278.2 

0.02827 

1.079 

176.6 

634.0 

0.3535 

1.1455 

707.7 

.2636 

770.5 

1.3503 

120 

286.4 

0.02836 

1.047 

179.0 

634  0 

0.3576 

1.1427 

708.2 

.2612 

771.3 

1.3479 

122 

294.8 

0.02846 

1.017 

181.4 

634.0 

0.3618 

1.1400 

708.6 

.2587 

772.0 

1.3455 

124 

303.4 

0.02855 

0.987 

183.9 

634.0 

0.3659 

1.1372 

709.1 

.2563 

772.8 

1.3431 

126 

312.2 

0.02865 

0.958 

186.3 

633.9 

0.3700 

1.1344 

709.6 

1.2538 

773.5 

1.3407 

128 

321.2 

0.02875 

0.931 

188.8 

633.9 

0.3741 

1.1316 

710.0 

1.2513 

774.2 

1.3383 

chloride,  water,  and  monofluorotrichloromethane  (Fn),  for  each  of 
which  a  tabl.e  is  presented.  Each  table  gives  the  principal  physical 
properties  of  the  saturated  substance,,  and  all  are  arranged  in  uniform 
fashion.  In  each  case  columns  are  included  which  give  the  heat  content 
and  entropy  of  the  superheated  vapor  at  two  selected  points.  Tables  1, 
2,  3  and  4  which  include  the  refrigerants  much  used  in  reciprocating  and 
rotary  mechanical  compression  systems  have  a  2  F  temperature  interval. 
As  water  and  JPu  are  much  used  in  centrifugal  compression  systems  the 
temperature  interval  in  Tables  5  and  6  is  5  F. 

AIR  DRYING  AGENTS 

Moisture  may  be  removed  from  air,  thus  accomplishing  dehumidi- 
fication,  by  the  use  of  any  one  of  a  number  of  substances  if  the  moist  air 
and  these  substances  are  brought  together  under  suitable  circumstances. 
One  class  of  these  substances  are  solids  at  ordinary  conditions  and  have 
the  power  of  adsorbing  the  moisture  from  the  air.  Another  class  of  air 
drying  agents  are  liquids  under  ordinary  conditions  and  absorb  the  mois- 
ture from  the  air.  Nearly  all  the  drying  agents  in  frequent  commercial 
use  in  air  conditioning  installations  are  of  one  or  the  other  of  these  two 
classes. 

Adsorbents 

These  substances  are  characterized  by  a  physical  structure  containing 
a  great  number  of  extremely  small  pores  but  still  retaining  sufficient 
mechanical  strength  to  resist  whatever  wear  and  handling  to  which  they 
are  subjected.  To  be  suitable  for  air  drying  purposes  they  must  be  widely 
available  at  economical  cost,  durable  in  use,  stable  in  form  and  properties, 
and  capable  of  withstanding  the  re-activation  processes  by  which  they  are 
made  ready  for  repeated  use.  They  must  also  possess  capacity  for 
adsorbing  and  holding  so  sufficient  a  quantity  of  moisture  that  the 
dimensions  of  the  beds  necessary  to  accommodate  them  will  be  practical. 

37 


HEATING  VENTILATING   AIR  CONDITIONING   GUIDE  1938 


TABLE  2,    PROPERTIES  OF  CARBON  DIOXIDE 


HEAT  CONTENT  AND  ENTROPY  TAKEN  FROM  —40  F 


&  p*-- 

^'     LB  PER 
*         SQ  Is. 

VOLUME 

Heat  Content 

Entropy 

50  F  Superheat 

100  F  Superheat 

Liquid         Vapor 

Liquid 

1 

Vapor 

Liquid 

Vapor 

Ht.  Ct. 

Entropy 

Ht.  Ct. 

Entropy 

0 

305.5  0.01570  0.29040 

18.8 

138.9 

0.0418 

0.3024 

153.7 

0.3342 

167.5 

0.3612 

315.9 

0.01579  0.28030 

19.8 

138.8 

0.0440 

0.3014 

153.7 

0.3330 

167.6 

0.3600 

4 

326.5 

0.01588  0.27070 

20.8 

138.8 

0.0461 

0.3005 

153.7 

0.3318 

167.7 

0.3588 

5 

332.0 

0.0159210.26610 

21.3 

138.8 

0.0472 

0.3000 

153.7 

0.3312 

167.7 

0.3582 

6 

337.4 

0.01596 

0.26140 

21.8 

138.7 

0.0483 

0.2994 

153.7 

0.3306 

167.8 

0.3576 

8 

348.7 

0.01605 

0.25260 

22.9 

138.7 

0.0504 

0.2982 

153.7 

0.3293 

167.9 

0.3563 

10 

360.2 

0.01614 

0.24370 

24.0 

138.7 

0.0526 

0.2970 

153.7 

0.3281 

168.0 

0.3550 

12 

371.9 

0.01623 

0.23540 

25.0 

138.6 

0.0548 

0.2958 

153.7 

0.3270 

168.1 

0.3538 

14 

383.9 

0.01632 

0.22740 

26.1 

138.6 

0.0571 

0.2946 

153.7 

0.3259 

168.2 

0,3526 

16 

396.2 

0.01642 

0.21970 

27.2 

138.5 

0.0593 

0.2933 

153.7 

0.3249 

168.3 

0.3513 

18 

408.9 

0.01652 

0.21210 

28.3 

138.4 

0.0616 

0.2921 

153.7 

0.3238 

168.5 

0.3501 

20 

421.8 

0.01663 

0.20490 

29.4 

138.3 

0.0638 

0.2909 

153.7 

0.3227 

168.6 

0.3489 

22 

434.0 

0.01673 

0.19790 

30.5 

138.2 

0.0662 

0.2897 

153.7 

0.3214 

168.7 

0.3479 

24 

448.410.01684 

0.19120 

31.7 

138.1 

0.0686 

0.2885 

153.7 

0.3202 

168.8 

0.3470 

26 

462.2 

0.01695 

0.18460 

32.9 

138.0 

0.0710 

0.2873 

153.7 

0.3189 

168.9 

0.3460 

28 

476.3 

0.01707 

0.17830 

34.1 

137.9 

0.0734 

0.2861 

153.7 

0.3177 

169.0 

0.3451 

30 

490.8 

0.01719 

0.17220 

35.4 

137.8 

0.0758 

0.2849 

153.7 

0.3164 

169.1 

0.3441 

32 

505.5 

0.01731 

0.16630 

36.7 

137.7 

0.0781 

0.2834 

153.7 

0.3158 

169.2 

0.3431 

34 

522.6 

0.01744 

0.16030 

37.9 

137.4 

0.0804 

0.2820 

153.7 

0.3151 

169.3 

0.3421 

36 

536.0 

0.01759 

0.15500 

39.1 

137.2 

0.0828 

0.2805 

153.7 

0.3145 

169.4 

0.3411 

38 

551.7 

0.01773 

0.14960 

40.4 

136.9 

0.0851 

0.2791 

153.7 

0.3138 

169.5 

0.3401 

39 

559.7 

0.01780 

0.14700 

41.0 

136.8 

0.0862 

0.2783 

153.7 

0.3135 

169.5 

0.3396 

40    i  567.8 

0.01787 

0.14440 

41.7 

136.7 

0.0874 

0.2776 

153.7 

0.3132 

169.6 

0.3391 

41 

576.0 

0.01794 

0.14185 

42.3 

136.5 

0.0887 

0.2768 

153.7 

0.3127 

169.6 

0.3386 

42 

584.3 

0.01801 

0.13930 

42.9 

136.3 

0.0899 

0.2761 

153.7 

0.3122 

169.7 

0.3381 

44 

601.1 

0.01817 

0.13440 

44.3 

136.1 

0.0924 

0.2745 

153.7 

0.3112 

169.8 

0.3371 

46 

618.2 

0.01834 

0.12970 

45.6 

135.7 

0.0950 

0.2730 

153.7 

0.3101 

169.9 

0.3362 

48 

635.710.01851 

0.12500 

47.0 

135.4 

0.0975 

0.2714 

153.7 

0.3091 

170.0 

0.3352 

50 

653.6 

0.01868 

0.12050 

48.4 

135.0 

0.1000 

0.2699 

153.7 

0.3081 

170.1 

0.3342 

52 

671.9 

0.01887 

0.11610 

49.8 

134.5 

0.1027 

0.2681 

153.7 

0.3069 

170.2 

0.3333 

54 

690.6 

0.01906 

0.11170 

51.2 

133.9 

0.1054 

0.2663 

153.7 

0.3057 

170.3 

0.3324 

56 

709.5 

0.01927 

0.10750 

52.6 

133.4 

0.1081 

0.2644 

153.7 

0.3046 

170.5 

0.3315 

58 

728.8 

0.01948 

0.10340 

54.0 

132.7 

0.1108 

0.2626 

153.7 

0.3034 

170.6 

0.3306 

60 

748.6 

0.01970 

0.09940 

55.5 

132.1 

0.1135 

0.2608 

153.7 

0.3022 

170.7 

0.3297 

62 

769.0 

0.01995 

0.09545 

57.0 

131.3 

0.1164 

0.2584 

153.7 

0.3012 

170.8 

0.3289 

64 

789.4 

0.02020 

0.09180 

58.6 

130.6 

0.1194 

0.2560 

153.7 

0.3002 

170.9 

0.3281 

66 

810.3 

0.02048 

0.08800 

60.2 

129.7 

0.1223 

0.2535 

153.7 

0.2991 

171.0 

0.3273 

68 

831.6 

0.02079 

0.08422 

61.9 

128.7 

0.1253 

0.2511 

153.7 

0.2981 

171.1 

0.3265 

70 

853.4 

0.02112 

0.08040 

63.7 

127.5 

0.1282 

0.2487 

153.7 

0.2971 

171.2 

0.3257 

72 

875.8 

0.02152 

0.07654 

65.5 

126.0 

0.1321 

0.2450 

153.7 

0.2962 

171.3 

0.3250 

74 

898.2 

0.02192 

0.07269 

67.3 

124.5 

0.1360 

0.2414 

153.7 

0.2953 

171.4 

0.3242 

76 

921.3 

0.02242 

0.06875 

69.4 

122.8 

0.1398 

0.2377 

153.7 

0.2945 

171.5 

0.3235 

78 

944.8 

0.02300 

0.06473 

71.6 

120.9 

0.1437 

0.2341 

153.7 

0.2936 

171.6 

0.3227 

80 

968.7 

0.02370 

0.06064 

73.9 

118.7 

0.1476 

0.2304 

153.7 

0.2927 

171.7 

0.3220 

82 

993.0 

0.02456 

0.05648 

76.4 

116.6 

0.1578 

0.2195 

153.7 

0.2920 

173.8 

0.3215 

84 

1017.7 

0.02553 

0.05223 

79.4 

113.9 

0.1679 

0.2087 

153.7 

0.2914 

176.0 

0.3209 

86 

1043.0 

0.02686 

0.04789 

83.3 

110.4 

0.1781 

0.1978 

153.7 

0.2907 

178.2 

0.3204 

87.8 

1069.9 

0.03454 

0.03454 

97.0 

97.0 

0.1880 

0.1880 

153.7 

0.2901 

180.1 

0.3199 

CHAPTER  2.   REFRIGERANTS  AND  AIR  DRYING  AGENTS 


Aluminum  Oxide,  (Alumina),  in  a  porous,  amorphous  form  is  a  solid 
adsorbent  frequently  called  by  the  common  name  activated  alumina,  and 
containing  small  amounts  of  hydrated  aluminum  oxide,  and  very  small 
amounts  of  soda,  and  various  metallic  oxides.  A  good  grade  of  activated 
alumina  will  show  92  per  cent  of  AkOz,  and  its  soda  content  will  be  com- 
bined with  silica  and  alumina  into  an  insoluble  compound.  This  substance 
also  has  the  property  of  adsorbing  certain  gases  and  certain  vapors  other 


"80          I2D         160         200" 
ENTERING  AIR  TEMPERATURE,  °F 

FIG.  1.    TEMPERATURE— VAPOR  PRESSURE— CONCENTRATION  RELATION  FOR  A 
SILICA  GEL  BED  AT  CONSTANT  TEMPERATURE 

than  water  vapor— a  property  which  is  sometimes  useful  in  air  condi- 
tioning installations.  It  is  available  commercially  in  granules  ranging 
trom  a  fine  powder  to  pieces  approximately  1.5  in.  in  diameter.  It  has 
iiigh  adsorptive  capacity  per  unit  of  weight,  and  is  non-toxic.  It  may  be 
repeatedly  re-activated  after  becoming  saturated  with  adsorbed  moisture 
without  practical  loss  of  its  adsorptive  ability.  In  the  grade  frequently 
US!i  °or^dTng  £e  re-activati<>n  may  be  accomplished  at  temperatures 
under  350  F.  Specific  gravity  is  3.25  and  the  pores  are  reported  to  occupy 
58  per  cent  of  the  volume  of  each  particle.  For  most  estimating  purposes 

39 


HEATING  VENTILATING   AIR  CONDITIONING   GUIDE  1938 


TABLE  3.    PROPERTIES  OF  DICHLORODIFLUOROMETHANE(FIO) 


HEAT  CONTENT  AND  ENTROPY  TAKEN  FROM  -40  F 


rlS;    *•* 

T|SP'     LBMB 
h         SQ!N. 

VOLUME         
1    Heat  Content 

Entropy 

25  F  Superheat 

50  F  Superheat 

Liquid      Vapor      Uquid  1  Vapor 

Liquid 

Vapor 

Ht.  Ct. 

Entropy 

Ht.  Ct. 

Entropy 

0    i  23.870.0110J  1.637     8.25 

78.21 

0.01869 

0.17091 

81.71 

0.17829 

85.26 

0.18547 

2       24  890.01101  1.5741    8.67 

78.44 

0.01961 

0.17075 

81.94 

0.17812 

85.51 

0.18529 

4 

25.960.0111    1.514     9.10 

i  78.67 

0.02052 

0.17060 

82.17 

0.17795 

85.76 

0.18511 

5      26.  510.0111!  1.485!    9.32   78.79 

0.02097 

0.17052 

82.29 

0.17786 

85.89 

0.18502 

6    !  27.050.0111    1.457 

9.53 

78.90 

0.02143 

0.17045 

82.41 

0.17778 

86.01 

0.18494 

8     '  28.180.0111J  1.403     9.96 

79.13 

0.02235 

0.17030 

82.66 

0.17763 

86.26 

0.18477 

10    :  29.350.0112   1.3511  10.39 

79.36 

0.02328 

0.17015 

82.90 

0.17747 

86.51 

0.18460 

12    ;  30.560.0112   1.301 

10.82 

79.59 

0.02419 

0.17001 

83.14 

0.17,733 

86.76 

0.18444 

14       31.800.0112    1.253 

11.26 

79.82 

0.02510 

0.16987 

83.38 

0.17720 

87.01 

0.18429 

16    !  33.0810.  0112 

1.207 

11.70 

80.05 

0.02601 

0.16974 

83.61 

0.17706 

87.26 

0.18413 

18    j  34.400.01131  1.163 

12.12 

80.27 

0.02692 

0.16961 

83.85 

0.17693 

87.51 

0.18397 

20      35.  75  0.0113|  1.121 

12.55 

80.49 

0.02783 

0.16949 

84.09 

0.17679 

87.76 

0.18382 

22    !  37.150.0113   1.081 

13.00 

80.72 

0.02873 

0.16938 

84.32 

0.17666 

88.00 

0.18369 

24       38.580.0113 

1.043 

13.44 

80.95 

0.02963 

0.16926 

84.55 

0.17652 

88.24 

0.18355 

26       40.070.0114 

1.007 

13.88 

81.17 

0.03053 

0.16913 

84.79 

0.17639 

88.49 

0.18342 

28      41.590.0114 

0.973 

14.32 

81.39 

0.03143 

0.16900 

85.02 

0.17625 

88.73 

0.18328 

30 

43.160.0115 

0.939 

14.76 

81.61 

0.03233 

0.16887 

85.25 

0.17612 

88.97 

0.18315 

32 

44.77 

0.0115 

0.908 

15.21 

81.83 

0.03323 

0.16876 

85.48 

0.17600 

89.21 

0.18303 

34 

46.420.0115 

0.877 

15.65 

82.05 

0.03413 

0.16865 

85.71 

0.17589 

89.45 

0.18291 

36      48.  13)0.0116 

0.848 

16.10 

82.27 

0.03502 

0.16854 

85.95 

0.17577 

89.68 

0.18280 

38      49.88^0.0116 

0.819 

16.55 

82.49 

0.03591 

0.16843 

86.18 

0.17566 

89.92 

0.18268 

39       50.780.0116 

0.806 

16.77 

82.60 

0.03635 

0.16838 

86-29 

0.17560 

90.04 

0.18262 

40    ;  51.680.0116 

0.792 

17.00 

82.71 

0.03680 

0.16833 

86.41 

0.17554 

90.16 

0.18256 

41    ;  52.70:0.0116 

0.779 

17.23 

82.82 

0.03725 

0.16828 

86.52 

0.17549 

90.28 

0.18251 

42       53.510.0116 

0.767 

17.46 

82.93 

0.03770 

0.16823 

86.64 

0.17544 

90.40 

0.18245 

44 

55.40)0.0117 

0.742 

17.91 

83.15 

0.03859 

0.16813 

86.86 

0.17534 

90.65 

0.18235 

46 

57.35 

0.0117 

0.718 

18.36 

83.36 

0.03948 

0.16803 

87.09 

0.17525 

90.89 

0.18224 

48 

59.35 

0.0117 

0.695 

18.82 

83.57 

0.04037 

0.16794 

87.31 

0.17515 

91.14 

0.18214 

50 

61.390.0118  0.673 

19.27 

83.78 

0.04126 

0.16785 

87.54 

0.17505 

91.38 

0.18203 

52 

63.49 

0.0118 

0.652 

19.72 

83.99 

0.04215 

0.16776 

87.76 

0.17496 

91.61 

0.18193 

54 

65.63jO.0118 

0.632 

20.18 

84.20 

0.04304 

0.16767 

87.98 

0.17486 

91.83 

0.18184 

56 

67.8410.  0119 

0.612 

20.64 

84.41 

0.04392 

0.16758 

88.20 

0.17477 

92.06 

0.18174 

58 

70.100.0119 

0.593 

21.11 

84.62 

0.04480 

0.16749 

88.42 

0.17467 

92.28 

0.18165 

60       72.41jO.0119 

0.575 

21.57 

84.82 

0.04568 

0.16741 

88.64 

0.17458 

92.51 

0.18155 

62    i  74.77 

0.0120 

0.557 

22.03 

85.02 

0.04657 

0.16733 

88.86 

0.17450 

92.74 

0.18147 

fri 

77.20 

0.0120 

0.540 

22.49 

85.22 

0.04745 

0.16725 

89.07 

0.17442 

92.97 

0.18139 

66       79.67 

0.0120 

0.524 

22.95 

85.42 

0.04833 

0.16717 

89.29 

0.17433 

93.20 

0.18130 

68       82.24 

0.0121 

0.508 

23.42 

85.62 

0.04921 

0.16709 

89.50 

0.17425 

93.43 

0.18122 

70 

84.82 

0.0121 

0.493 

23.90 

85.82 

0.05009 

0.16701 

89.72 

0.17417 

93.66 

0.18114 

72    !  87.50 

0.0121 

0.479 

24.37 

86.02 

0.05097 

0.16693 

89.93 

0.17409 

93.99 

0.18106 

74       90.20 

0.0122 

0.464 

24.84 

86.22 

0.05185 

0.16685 

90.14 

0.17402 

94.12 

0.18098 

76       93.00 

0.0122 

0.451 

25.32 

86.42 

0.05272 

0.16677 

90.36 

0.17394 

94.34 

0.18091 

78      95.85 

0.0123 

0.438 

25.80 

86.61 

0.05359 

0.16669 

90.57 

0.17387 

94.57 

0.18083 

80      98.76 

0.0123 

0.425 

26.28 

86.80 

0.05446 

0.16662 

90.78 

0.17379 

94.80 

0.18075 

82    1101.70 

0.0123 

0.413 

26.76 

86.99 

0.05534 

0.16655 

90.98 

0.17372 

95.01 

0.18068 

84    il04.S 

0.0124 

0.401 

27.24 

87.18 

0.05621 

0.16648 

91.18 

0.17365 

95.22 

0.18061 

86    i!07.9 

0.0124 

0.389 

27.72 

87.37 

0.05708 

0.16640 

91.37 

0.17358 

95.44 

0.18054 

88 

111,1 

0.0124 

0.378 

28.21 

87.56 

0.05795 

0.16632 

91.57 

0.17351 

95.65 

0.18047 

90 

114.3 

0.0125 

0.368 

28.70 

87.74 

0.05882 

0.16624 

91.77 

0.17344 

95.86 

0.18040 

92 

117.7 

0.0125   0.357 

29.19 

87.92 

0.05969 

0.16616 

91.97 

0.17337 

96.07 

0.18033 

94 

121.0 

0.0126  0.347 

29.68 

88.10 

0.06056 

0.16608 

92.16 

0.17330 

96.28 

0.18026 

96 

124.5 

0.0126 

0.338 

30.18 

88.28 

0.06143 

0.16600 

92.36 

0.17322 

96  50 

0.18018 

98     128.0 

0.0126 

0.328 

30.67 

88.45 

0.06230 

0.16592 

92.55 

0.17315 

96.71 

0.18011 

100    J131.6 

0.0127 

0.319 

31.16 

88.62 

0.06316 

0.16584 

92.75 

0.17308 

96.92 

0  18004 

102 

135.3 

0.0127 

0.310 

31.65 

88.79 

0.06403 

0.16576 

92.93 

0.17301 

97.12 

0.17998 

40 


CHAPTER  2.   REFRIGERANTS  AND  AIR  DRYING  AGENTS 


TABLE  3.    PROPERTIES  OF  DICHLORODIFLUOROMETHANE  (Fi2) — Continued 


SAT. 
TEMP. 
F 

ABS 
PRESS. 
LB  PER 
SQ!N. 

VOLUME 

HEAT  CONTENT  AND  ENTROPY  TAKEN  FBOM  —40  F 

Heat  Content 

Entropy 

25  F  Superheat 

SO  F  Superheat 

Liquid 

Vapor 

Liquid 

Vapor 

Liquid 

Vapor 

Ht.  Ct. 

Entropy 

Ht  Ct. 

Entropy 

104 

139.0 

0.0128 

0.302 

32.15 

88.95 

0.06490 

0.16568 

93.11 

0.17294 

97.32 

0.17993 

106 

142.8 

0.0128 

0.293 

32.65 

89.11 

0.06577 

0.16560 

93.30 

0.17288 

97.53 

0.17987 

108 

146.8 

0.0129 

0.285 

33.15 

89.27 

0.06663 

0.16551 

93.48 

0.17281 

97.73 

0.17982 

110 

150.7 

0.0129 

0.277 

33.65 

89.43 

0.06749 

0.16542 

93.66 

0.17274 

97.93 

0.17976 

112 

154.8 

0.0130 

0.269 

34.15 

89.58 

0.06836 

0.16533 

93.82 

0.17266 

98.11 

0.17969 

114 

158.9 

0.0130 

0.262 

34.65 

89.73 

0.06922 

0.16524 

93.98 

0.17258 

98.29 

0.17961 

116 

163.1 

0.0131 

0  254 

35.15 

89.87 

0.07008 

0.16515 

94.15 

0.17249 

98.4810.17954 

118 

167.4 

0.0131 

0.247 

35.65 

90.01 

0.07094 

0.16505 

94.31 

0.17241 

98.66 

0.17946 

120 

171.8 

0.0132 

0.240 

36.16 

90.15 

0.07180 

0.16495 

94.47 

0.17233 

98.84 

0.17939 

122 

176.2 

0.0132 

0.233 

36.66 

90.28 

0.07266 

0.16484 

94.63 

0.17224 

99.01 

0.17931 

124 

180.8 

0.0133 

0.227 

37.16 

90.40 

0.07352 

0.16473 

94.78 

0.17215 

99.18 

0.17922- 

126 

185.4 

0.0133 

0.220 

37.67 

90.52 

0.07437 

0.16462 

94.94 

0.17206 

99.35 

0.17914 

128 

190.1 

0.0134 

0.214 

38.18 

90.64 

0.07522 

0.16450 

95.09 

0.17196 

99.53 

0.17906 

130 

194.9 

0.0134 

0.208 

38.69 

90.76 

0.07607 

0.16438 

95.25 

0.17186 

99.70 

0.17897 

132 

199.8 

0.0135 

0.202 

39.19 

90.86 

0.07691 

0.16425 

95.41 

0.17176 

99.87 

0.17889 

134 

204.8 

0.0135 

0.196 

39.70 

90.96 

0.07775 

0.16411 

95.56 

0.17166 

100.04 

0.17881 

136 

209.9 

0.0136 

0.191 

40.21 

91.06 

0.07858 

0.16396 

95.72 

0.17156 

100.22 

0.17873 

138 

215.0 

0.0137 

0.185 

40.72 

91.15 

0.07941 

0.16380 

95.87 

0.17145 

100.39 

0.17864 

140 

220.2 

0.0138 

0.180 

41.24 

91.24 

0.08024 

0.16363 

96.03 

0.17134 

100.56 

0.17856 

the  volume-weight  relation  on  a  dry  basis  may  be  taken  as  50  Ib  per  cubic 
foot  although  in  the  smaller  sizes  the  packed  weight  may  be  as  much  as 
64  Ib  per  cubic  foot. 

Silicon  Dioxide,  (Silica),  in  a  special  form  obtained  by  suitably  mixing 
sulphuric  acid  with  sodium  silicate,  is  another  solid  adsorbent  and  is 
commonly  called  silica  gel.  Its  capillary  structure  is  exceedingly  small, 
so  small  that  its  exact  structure  has  to  be  deduced  rather  than  observed. 
The  gel  is  available  commercially  in  a  wide  variety  of  sizes  of  granules 
ranging  from  4  to  300  mesh.  It  has  high  adsorptive  capacity  per  unit 
of  weight  and  is  non-toxic,  may  be  repeatedly  re-activated  without 
practical  deterioration.  Re-activation  may  be  accomplished  at  tem- 
peratures of  air  up  to  600  F  although  it  is  frequently  accomplished  with 
air  or  other  gases  at  temperatures  not  over  350  F.  Volume  of  the  capillary 
pores  is  reported  to  be  from  50  to  70  per  cent  of  the  total  solid  volume. 
For  most  estimating  purposes  the  volume-weight  relation  can  be  assumed 
as  from  38  to  40  Ib  per  cubic  foot  on  a  dry  basis. 

Other  substances  having  properties  which  make  them  available  as 
solid  adsorbents  include  lamisilate  and  charcoal  but  details  of  their 
physical  properties  are  not  available. 

Nature  of  Adsorption  Process 

Adsorption  is  accomplished  without  chemical  change  between  the  air 
and  the  adsorbent  substance.  The  adsorbent  does  not  go  into  solution  but 
water  vapor  is  extracted  from  the  air-vapor  stream  passing  through  the 
bed  of  adsorbent  material  and  is  caught  and  retained  in  the  capillary 
pores.  The  exact  nature  of  the  process  which  goes  on  during  adsorption 

41 


HEATING  VENTILATING  AIR  CONDITIONING   GUIDE  1938 


TABLE  4.    PROPERTIES  OF  METHYL  CHLORIDE 


HEAT  CONTEST  AND  ENTROPY  TAKEN  FROM  -40  F 


F           SslN? 

I 

VoL-nos           •  
I                                     Heat  Content     '        Entropy 

100  F  Superheat 

200  F  Superheat 

Liquid    ;'    Vapor       Liquid      Vapor 

Liquid 

Vapor 

Ht.  Ct. 

Entropy 

Ht.  Ct. 

Entropy 

0       18.73  0.0162  :   5.052     14,4     192.4 

0.0328 

0.4197 

215.6 

0.467 

237.2 

0.507 

2       19.60  0.0162      4.856     15.1  i  193.1 

0.0344 

0.4196 

216.2 

0.466 

237.7 

0.505 

4    I  20.47  0.0163  ,   4.661     15.8 

193.80.0360 

0.4195 

216.7 

0.465 

238.2 

0.504 

5    i  20.91:0.0163 

4.563     16.2 

194.1 

0.0368 

0.4195 

217.0 

0.464 

238.5 

0.503 

6 

21.  39;  0.0163      4.476     16.6 

194.4 

0.0376 

0.4194 

217.3 

0.464 

238.8 

0.502 

8 

22.  34'  0.0164 

4.303     17.3 

195.1 

0.0391 

0.4193 

217.9 

0.463 

239.4 

0.501 

10 

23.30  0.0164 

4.129     18.1 

195.8 

0.0407 

0.4192 

218.5 

0.463 

240.0 

0.500 

12 

24.38  0.0164  '  3.984     18.8 

196.3 

0.0423 

0.4184 

219.0 

0.462 

240.5 

0.499 

14 

25.46  0.0164      3.839     19.6 

196.7 

0.0439 

0.4176 

219.5 

0.462 

241.0 

0.498 

16 

26.55  0,0165      3.693 

20.3 

197.2 

0.0454 

0.4168 

220.0 

0.461 

241.5 

0.498 

18 

27.  63'  0.0165 

3.548 

21.1 

197.6 

0.0472 

0.4160 

220.5 

0.461 

242.0 

0.497 

20 

28.  71!  0.0166 

3.403 

21.8 

198.1 

0.0486 

0.4152 

221.0 

0.460 

242.5 

0.496 

22 

29.98  0.0166 

3.288 

22.5 

198.5 

0.0501 

0.4148 

221.5 

0.459 

243.0 

0.495 

24 

31.25  0.0166 

3.172 

23.3 

198.9 

0.0516 

0.4143 

222.0 

0.459 

243.6 

0.495 

26 

32.53  0.0167 

3.057 

24.0 

199.3 

0.0532 

0.4139 

222.4 

0.458 

244.1 

0.494 

28 

33.  801  0.0167 

2.941 

24.8 

199.7 

0.0547 

0.4134 

222.9 

0.458 

244.7 

0.494 

30 

35.  0/1  0.0168 

2.826 

25.5 

200.1 

0.0562 

0.4130 

223.4 

0.457 

245.2 

0.493 

32       36.55 

0.0168 

2.734 

26.2 

200.5 

0.0577 

0.4124 

223.9 

0.456 

245.7 

0.492 

34 

38.03  0.0169 

2.642 

27.0 

200.9 

0.0592 

0.4118 

224.3 

0.455 

246.2 

0.492 

36 

39.5110.0169 

2.549 

27.7 

201.4 

0.0607 

0.4111 

224.8 

0.455 

246.7 

0.491 

38 

40.99 

0.0169 

2.457 

28.5 

201.8 

0.0622 

0.4105 

225.2 

0.454 

247.2 

0.491 

39 

41.73 

0.0170 

2.411 

28.8 

202.0 

0.0629 

0.4102 

225.5 

0.453 

247.4 

0.490 

40 

42.47 

0.0170 

2.365 

29.2 

202.2 

0.0637 

0.4099 

225.7 

0.453 

247.7 

0.490 

41 

43.33 

0.0170 

2.328 

29.6 

202.4 

0.0644 

0.4096 

225.9 

0.453 

248.0 

0.490 

42 

44.18 

0.0171 

2.290 

29.9 

202.6 

0.0651 

0.4093 

226.1 

0.452 

248.3 

0.489 

44 

45.89 

0.0171 

2.216 

30.7 

203.0 

0.0666 

0.4087 

226.6 

0.451 

248.8 

0.489 

46 

47.61 

0.0171 

2.141 

31.4 

203.3 

0.0680 

0.4081 

227.0 

0.451 

249.4 

0.488 

48 

49.32 

0.0172 

2.067 

32.2 

203.7 

0.0695 

0.4075 

227.5 

0.450 

249.9 

0.488 

50 

51.03 

0.0172 

1.992 

32.9 

204.1 

0.0709 

0.4069 

227.9 

0.449 

250.5 

0.487 

52 

53.00 

0.0172 

1.931 

33.7 

204.4 

0.0724 

0.4063 

228.2 

0.448 

251.0 

0.486 

54 

54.97 

0.0173 

1.870 

34.4 

204.7 

0.0739 

0.4056 

228.6 

0.448 

251.5 

0.486 

56 

56.94 

0.0173 

1.810 

35.2 

205.1 

0.0754 

0.4050 

228.9 

0.447 

252.0 

0.485 

58 

58.91 

0.0173 

1.749 

35.9 

205.4 

0.0769 

0.4043 

229.3 

0.447 

252.5 

0.485 

60 

60.88 

0.0174 

1.688 

36.7 

205.7 

0.0784 

0.4037 

229.6 

0.446 

253.0 

0.484 

62 

63.13 

0.0174 

1.638 

37.4 

206.0 

0.0798 

0.4030 

229.9 

0.445 

253.5 

0.483 

64 

65.37 

0.0174 

1.588 

38.2 

206.3 

0.0812 

0.4024 

230.3 

0.444 

254.0 

0.483 

66 

67.62 

0.0175 

1.539 

38.9 

206.6 

0.0827 

0.4017 

230.6 

0.443 

254.5 

0.482 

68 

69.86 

0.0175 

1.489 

39.7 

206.9 

0.0841 

0.4011 

231.0 

0.442 

255.0 

0.482 

70 

72.11 

0.0176 

1.439 

40.4 

207.2 

0.0855 

0.4004 

231.3 

0.441 

255.5 

0.481 

72 

74.66 

0.0176 

1.398 

41.1 

207.5 

0.0869 

0.3998 

231.6 

0.440 

256.0 

0.480 

74 

77.21 

0.0177 

1.357 

41.9 

207.7 

0.0883 

0.3992 

232.0 

0.439 

256,5 

0.480 

76 

79.76 

0.0177 

1.315 

42.6 

208.0 

0.0898 

0.3985 

232.3 

0.439 

256.9 

0.479 

78 

82.31 

0.0178 

1.274 

43.4 

208.2 

0.0912 

0.3979 

232.7 

0.438 

257.4 

0.479 

80 

84.86 

0.0178 

1.233 

44.1 

208.5 

0.0926 

0.3973 

233.0 

0.437 

257.9 

0.478 

82 

87.74 

0.0178 

1.199 

44.8 

208.7 

0.0940 

0.3967 

233.3 

0.436 

258.4 

0.478 

84 

90.62 

0.0179 

1.165 

45.6 

209.0 

0.0953 

0.3960 

233.6 

0.435 

258.9 

0.477 

86 

93.50 

0.0179 

1.130 

46.3 

209.2 

0.0967 

0.3954 

233.9 

0.435 

259.4 

0.477 

88 

96.38 

0.0180 

1.096 

47.1 

209.5 

0.0980 

0.3947 

234.2 

0.434 

259.9 

0.476 

90 

99.26 

0.0180 

1.062 

47.8 

209.7 

0.0994 

0.3941 

234.5 

0.433 

260.4 

0.476 

92 

102.49 

0.0180 

1.033 

48.6 

209.9 

0.1008 

0.3935 

234.8 

0.433 

260.8 

0.476 

94 

105.72 

0.0181 

1.005 

49.3 

210.2 

0.1022 

0.3929 

235.1 

0.432 

261.2 

0.475 

96 

108.94 

0.0181 

0.9764 

50.1 

210.4 

0.1035 

0.3922 

235.4 

0.432 

261.6 

0.475 

98 

112.17 

0.0182 

0.9478 

50.8 

210.7 

0.1049 

0.3916 

235.7 

0.431 

262  0 

0.474 

100 

115.40 

0.0182 

0.9193 

51.6 

210.9 

0.1063 

0.3910 

236.0 

0.431 

262.4 

0^474 

102 

119.00 

0.0183 

0.8952 

52.3 

211.1 

0.1076 

0.3903 

236.4 

0.430 

262.8 

0.474 

42 


CHAPTER  2.   REFRIGERANTS  AND  AIR  DRYING  AGENTS 


TABLE  4.    PROPERTIES  OF  METHYL  CHLORIDE — (Continued) 


HEAT  CONTENT  AND  ENTBOPY  TAKES  FBOJI  —  40  F 

O.m 

ABS 

VOTTTMTS 

TEMP. 
F 

PRESS. 
LB  PER 
SQ  IN. 

Heat  Content 

Entropy 

100  F  Superheat 

200  F  Superheat 

Liquid 

Vapor 

Liquid 

Vapor 

Liquid 

Vapor 

Ht.  Ct. 

Entropy 

HtCt 

Entropy 

104 

122.60 

0.0183 

0.8712 

53.1 

211.3 

0.1090 

0.3897 

236.8 

0.430 

263.2 

0.473 

106 

126.20 

0.0184 

0.8471 

53.8 

211.4 

0.1103 

0.3890 

237.1 

0.429 

263.5 

0.473 

108 

129.80 

0.0184 

0.8231 

54.6 

211.6 

0.1117 

0.3884 

237.5 

0.429 

263.9 

0.472 

110 

133.40 

0.0185 

0.7990 

55.3 

211.8 

0.1130 

0.3877 

237.9 

0.428 

264.3 

0.472 

112 

137.42 

0.0185 

0.7786 

56.1 

212.0 

0.1144 

0.3871 

238.1 

0.427 

264.6 

0.471 

114 

141.44 

0.0185 

0.7583 

56.8 

212.2 

0.1157 

0.3864 

238.3 

0.427 

264.8 

0.470 

116 

145.46 

0.0186 

0.7379 

57.6 

212.4 

0.1171 

0.3858 

238.6 

0.426 

265.1 

0.470 

118 

149.48 

0.0186 

0.7176 

58.3 

212.6 

0.1184 

0.3851 

238.8 

0.426 

265.3 

0.469 

120 

153.50 

0.0187 

0.6972 

59.1 

212.8 

0.1198 

0.3845 

239.0 

0.425 

265.6 

0.468 

is  not  known  but  it  is  stated  that  the  action  is  brought  about  by  surface 
condensation,  and  also  by  a  difference  between  the  vapor  pressure  of  the 
water  condensing  inside  the  pores  and  the  partial  pressure  of  the  water 
vapor  in  the  air-vapor  mixture.  The  adsorbing  process  in  the  bed  can 
continue  until  the  vapor  pressures  come  into  equilibrium.  The  amount 
of  vapor  adsorbed  will  depend  on  the  adsorbent  substances  being  used 
but  for  any  single  substance  the  amount  depends  on  the  temperature  of 
the  bed  as  well  as  on  the  partial  pressure  of  the  air-vapor  mixture  being 
passed  over  it. 

As  the  process  of  adsorption  goes  on  heat  is  liberated  in  the  bed.  The 
heat  so  liberated  is  the  latent  heat  of  the  water  vapor  condensed  together 
with  the  so-called  heat  of  wetting.  For  a  pound  of  water  vapor  at  60  F 
the  latent  heat  released  by  condensation  is  approximately  1057  Btu. 
The  heat  of  wetting  for  silica  gel,  for  example,  is  about  200  Btu,  making  a 
total  heat  of  adsorption  of  approximately  1257  Btu  per  pound  of  water 
adsorbed  from  the  air-vapor  mixture  passing  through  the  silica  gel  bed. 
The  heat  of  wetting  varies  with  the  substance  being  used  as  the  adsorbent 
while  the  latent  heat  of  condensation  depends  only  on  the  temperature 
and  pressure  of  the  water  vapor. 

Temperature-Pressure-Concentration  Relations 

Since  the  adsorptive  ability  of  an  adsorbent  depends  on  the  temperature 
of  the  bed  and  on  the  partial  pressure  difference  between  the  pores  and  the 
air-vapor  mixture  it  is  important  to  know  the  pressures  and  temperatures 
at  which  pressure  equilibrium  is  reached. 

Evidently  the  equilibrium  conditions  represent  the  limits  beyond 
which  adsorption  of  vapor  cannot  continue.  The  relationship  can  be 
shown  graphically  and  Fig.  1  is  such  a  chart  for  silica  gel.  Charts  of  like 
nature  can  be  plotted  for  other  adsorbent  materials. 

Fig,  1  shows  the  equilibrium  conditions  for  a  gel  bed  maintained  at 
constant  temperature  while  the  water  vapor  adsorption  is  allowed  to 
continue  until  pressure  equilibrium  is  reached.  Each  curve  on  the  chart 
show  a  certain  dew-point  temperature,  and  therefore  a  certain  pressure, 
of  the  saturated  water  vapor. 

43 


HEATING   VENTILATING  .  AIR  CONDITIONING   GUIDE  1938 


TABLE  5.    PROPERTIES  OF  MONOFLUOROTRICHLOROMETHANE  (Fn) 


SAT. 
Tin*. 
F 

ABS 
PRKS. 
LB  PIE 
Sal*. 

i          VOLUME 

MTCAT  UONCTNT  AND  .ttNTBOPY  TAKEN  i?  BOM  —40  JB 

i    Heat  Content 

Entropy 

25  F  Superheat 

SO  F  Superheat 

;    Liquid    j     Vapor     !  Liquid      Vapor 

Liquid 

Vapor 

Ht.  Ct. 

Entropy 

Ht.  Ct. 

Entropy 

0 

2.  59J  0.01020!  13.  700 

7.81 

90.4 

0.0178 

0.1975 

93.9 

0.2049 

97.4 

0.2120 

5    ;   2.9610.01024S12.100 

8.81 

91.2 

0.0200 

0.1974 

94.7 

0.2047 

98.2 

0.2117 

10    :   3.  38  i  0.01028!  10.700 

9.82 

92.0 

0.0222 

0.1973 

95.5 

0.2045 

99.0 

0.2114 

15 

3.85 

0.010321   9.530 

10.80 

92.8 

0.0243 

0.1971 

96.3 

0.2043 

99.8 

0.2111 

20 

4.3610.01036!   8.490 

11.90 

93.7 

0.0264 

0.1970 

97.2 

0.2041 

100.7 

0.2109 

25 

4.94 

0.01040 

7.580 

12.90 

94.5 

0.0286 

0.1969 

98.0 

0.2039 

101.5 

0.2107 

30 

5.57 

0.01045 

6.770 

13.90 

95.3 

0.0307 

0.1969 

98.8 

0.2038 

102.3 

0.2105 

35        6.2710.01049 

6.080 

14.90 

96.1 

0.0328 

0.1968 

99.6 

0.2037 

103.1 

0.2103 

40 

7.03  0.01053 

5.460 

16.00 

96.8 

0.0349 

0.1968 

100.3 

0.2036 

103.8 

0.2101 

45 

7.88 

0.01057 

4.920 

17,00 

97.6 

0.0370 

0.1967 

101.1 

0.2035 

104.6 

0.2099 

50 

8.79 

0.01062 

4.440 

18.10 

98.4 

0.0391 

0.1967 

101.9 

0.2034 

105.4 

0.2098 

55 

9.80 

0.01066 

4.020 

19.10 

99.2 

0.0412 

0.1967 

102.7 

0.2033 

106.2 

0.2097 

60 

10.90 

0.01071 

3.640 

20.20 

100.0 

0.0432 

0.1967 

103.5 

0.2033 

107.0 

0.2096 

65 

12.10 

0.01076 

3.300 

21.30 

100.8 

0.0453 

0.1967 

104.3 

0.2032 

107.8 

0.2094 

70 

13.40 

0.01081 

3.000 

22.40 

101.5 

0.0473 

0.1967 

105.0 

0.2032 

108.5 

0.2093 

75 

14.80 

0.01086 

2.740 

23.50 

102.2 

0.0493 

0.1967 

105.7 

0.2031 

109.2 

0.2092 

80 

16.30 

0.01091 

2.500 

24.50 

102.9 

0.0513 

0.1966 

106.4 

0.2030 

109.9 

0.2090 

85 

17.90 

0.01096 

2.280 

25.60 

103.6 

0.0533 

0.1966 

107.1 

0.2029 

110.6 

0.2089 

90 

19.70 

0.01101 

2.090 

26.70 

104.4 

0.0553 

0.1966 

107.9 

0.2028 

111.4 

0.2088 

95 

21.60 

0.01106 

1.918 

27.80 

105.1 

0.0573 

0.1966 

108.6 

0.2028 

112.1 

0.2087 

100 

23.60 

0.01111 

1.761 

28.90 

105.7 

0.0593 

0.1965 

109.2 

0.2027 

112.7 

0.2085 

105 

25.90 

0.01116 

1.620 

30.10 

106.4 

0.0613 

0.1965 

109.9 

0.2026 

113.4 

0.2084 

As  an  example  in  the  interpretation  of  the  chart  consider  the  case  when 
moist  air  at  a  temperature  of  80  F  and  a  partial  vapor  pressure  of  0.5  in 
of  mercury  flows  through  a  bed  of  silica  gel  which  is  at  a  temperature  of 
80  F.  The  chart  indicates  that  the  equilibrium  of  pressure  between  the 
air-vapor  mixture  and  the  bed  is  reached  when  the  dry  bed  has  adsorbed 
moisture  to  the  extent  of  31  per  cent  of  the  weight  when  dry.  When  this 
happens  the  bed  can  adsorb  no  more  moisture  unless  its  temperature 
is  changed. 

In  practice  however  the  adsorbent  bed  is  seldom  held  at  a  steady  tem- 
perature in  air  conditioning  applications  and  neither  is  the  adsorption 
process  permitted  to  continue  until  moisture  equilibrium  is  reached 
Instead,  the^bed  temperature  varies  and  the  bed  is  re-activated  before 
equilibrium  is  approached.  While  charts  of  this  kind  can  show  the 
limiting  properties  of  the  substances  they  are  seldom  directly  applicable 
to  the  solution  of  air  conditioning  problems  unless  considerable  additional 
information  is  available.  This  takes  the  form  of  performance  data  cover- 
ing the  characteristics  of  the  equipment  in  which  the  adsorbent  bed  is 
placed.  Such  performance  data  are  beyond  the  scope  of  this  chapter. 

Liquid  Absorbents 

Any  absorbent  substance  may  be  used  as  an  air  drying  agent  if  it  has  a 

JS^wCTSf  loW*Vhan.  the  7aP°r  P«^re  in  the  i-vapor  mixture 
from  which  the  moisture  is  to  be  removed.  Absorbents  are  character- 
istically water  solutions  of  materials  in  which  the  vapor  pressure  is 

44 


CHAPTER  2.   REFRIGERANTS  AND  AIR  DRYING  AGENTS 


reduced  to  a  suitable  level  by  governing  the  concentration  of  the  solution. 
In  addition  to  haying  a  suitable  low  vapor  pressure,  a  practical  absorbent 
must  also  be  widely  available  at  economical  cost,  be  non-corrosive, 
odorless,  non-toxic,  chemically  inert  against  any  impurities  in  the  air 
stream,  stable  over  the  range  of  use  and  especially  it  must  not  precipitate 
out  at  the  lowest  temperature  to  which  the  apparatus  is  exposed.  It  must 
have  low  viscosity  and  be  capable  of  being  economically  regenerated  or 
concentrated  after  having  been  diluted  by  absorbing  moisture. 

Water  solutions,  or  brines,  of  the  chlorides  of  various  inorganic  elements 
such  as  calcium  chloride  and  lithium  chloride  are  the  absorbents  most 
frequently  used  in  connection  with  air  conditioning  applications  and  de- 
tailed attention  is  confined  to  these  two  in  this  chapter. 

Nature  of  Absorption  Process 

The  application  consists  of  bringing  the  air-vapor  stream  into  intimate 
contact  with  the  absorbent,  permissably  by  passing  the  air  stream  through 
a  finely  divided  spray  of  the  brine  but  more  generally  by  passing  the  air 
over  a  metal  surface  coil  where  the  liquid  absorbent  presents  a  large 
surface  to  the  air  stream.  The  difference  in  vapor  pressures  causes  some 
of  the  vapor  in  the  air-vapor  mixture  to  migrate  into  the  brine.  Here  it 
condenses  into  liquid  water  and  decreases  the  concentration  of  the  absor- 
bent. In  order  that  the  process  be  continuous  means  must  be  provided 
for  counteracting  the  diluting  effect  of  the  extracted  moisture  and  also  for 
maintaining  the  temperature  of  the  brine  sufficiently  low  to  hold  the 
desired  vapor  pressure. 

As  the  water  vapor  is  added  to  the  absorbent  and  condenses,  it  gives  up 
its  latent  heat  of  condensation  which  tends  to  raise  the  temperature  of 
both  the  absorbent  and  the  moist  air  stream.  For  every  pound  of  water 
absorbed  and  condensed  the  heat  added  to  the  air  stream  and  the  brine 

TABLE  6.    PROPERTIES  OF  WATER 


SAT. 
TEMP. 
F 

ABS 
PRESS. 
LB  PER 
3d  IN. 

VOLUME 

HEAT  CONTENT  AND  ENTROPY  TAKEN  FBOM  -1-32  F 

Heat  Content 

Entropy 

50  F  Superheat 

100  F  Superheat 

Liquid 

Vapor 

Liquid 

Vapor 

Liquid 

Vapor 

HtCt. 

Entropy 

HtOL 

Entropy 

32 

0.0887 

0.01602 

3296.0 

0.00 

1073.0 

0.0000 

2.1826 

1096.9 

2.2277 

1120.8 

2.2688 

35 

0.1000 

0.01602 

2941.0 

3.02 

1074.4 

0.0062 

2.1724 

1098.3 

2.2172 

1122.2 

2.2581 

40 

0.1217 

0.01602 

2441.0 

8.05 

1076.8 

0.0163 

2.1555 

1100.6 

2.2000 

1124.5 

2.2406 

45 

0.1475 

0.01602 

2034.0 

13.07 

1079.2 

0.0262 

2.1390 

1102.9 

2.1832 

1126.7 

2.2234 

50 

0.1780 

0.01602 

1702.0 

18.08 

1081.5 

0.0361 

2.1230 

1105.2 

2.1667 

1129.0 

2.2066 

55 

0.2140 

0.01603 

1430.0 

23.08 

1083.9 

0.0459 

2.1073 

1107.5 

2.1506 

1131.3 

2.1902 

60 

0.2561 

0.01603 

1206.0 

28.08 

1086.2 

0.0556 

2.0920 

1109.8 

2.1349 

1133.5 

2.1742 

65 

0.3054 

0.01604 

1021.0 

33.08 

1088.6 

0.0652 

2.0771 

1112.2 

2.1196 

1135.8 

2.1585 

70 

0.3628 

0.01605 

868.0 

38.07 

1090.9 

0.0746 

2.0625 

1114.5 

2.1046 

1138.1 

2.1432 

75 

0.4295 

0.01606 

740.0 

43.06 

1093.2 

0.0840 

2.0483 

1116.7 

2.0900 

1140.3 

2.1283 

80 

0.507 

0.01607 

632.9 

48.05 

1095.5 

0.0933 

2.0344 

1119.0 

2.0758 

1142.5 

2.1138 

85 

0.596 

0.01609 

543.3 

53.04 

1097.8 

0.1025 

2.0208 

1121.2 

2.0619 

1144.7 

2.0996 

90 

0.698 

0.01610 

467.9 

58.03 

1100.0 

0.1116 

2.0075 

1123.4 

2.0483 

1146.8 

2.0857 

95 

0.815 

0.01612 

404.2 

63.01 

1102.3 

0.1206 

1.9946 

1125.6 

2.0350 

1148.9 

2.0721 

100 

0.949 

0.01613 

350.3 

68.00 

1104.6 

0.1296 

1.9819 

1127.9 

2.0220 

1151.1 

2.0588 

105 

1.101 

0.01615 

304.4 

72.98 

1106.8 

0.1384 

1.9695 

1130.2 

2.0093 

1153.2 

2.0458 

For  properties  of  steam  at  high  temperatures,  see  Page  28. 

45 


HEATING  VENTILATING   AIR  CONDITIONING   GUIDE  1938 


TABLE  7.    DEW-POINT  OF  AIR  IN  EQUILIBRIUM  WITH  LITHIUM  CHLORIDE  SOLUTIONS 
CONCENTRATION*  IN  GRAM  MOLS  OF  LITHIUM  CHLORIDE  PER  1000  GRAINS  WATER 


o.o    2.0  ,  4.0     6.0 


5.0 


10.0 


12.0         14.0       16.0  ,  18.0  !  20.0  !  22.0  j  24.0  !  26.0  J  28.0  ,  30.0 


320315.2308,7 

299.9 

290.2 

279.7 

269.4 

259.6251.5244.1236.5,230.0223.8218.6214.5210.3 

300295.4289.1 

280.5 

270.9 

260.6 

250.5 

240.8232.6225.4218.0211.8i205.8200.8196.9,192.8 

280;275.6269.5261.1 

251.7 

241.5 

231.6 

222.2  214.0206.7,199.7  193.5187.8  183.2179.3)175.2 

260255.8250.0241.9 

232.6 

222.7 

212.8 

203.5  195.5188.4  181.7:175.41170.0  165.6'162.0  158.4 

240236.0230.4222.5 

213.5 

203.8 

194.2 

185.0177.1  170.0,163.6157.5'152.21148.3  144.6140.5 

220216.2210.8203.2 

194.4 

184.9 

175.5 

166.4  158.6  151  .6  145.3139.6  134.6,130.7  127.3124.2 

200196.41191-2 

183.9 

175.4 

166.1 

156.7 

148.0  140.3  133.5,127.3;121.9!117.0113.3  110.1 

180  176.6;171.6  164.7 

146.4 

147.3 

138.1 

129.6  122.1;115.5  109.4  104.2|  99.6  96.0,         i 

160:156.8,152.1 

;i45.4 

137.4 

128.6 

119.7 

111.3103.9,  97.4  91.61  86.61  82.21 

140137.0132.6 

126.1 

118.4 

109.9 

101.3 

93.1 

85.9,  79.5  73.8|  69.0'         ; 

120J117.2  113.0  106.8 

99.4 

91.1 

82.7 

74.71  67.8;  61.5!  56.0:         '         ;         [ 

110107.3il03.2l  97.2 

89.9 

81.9 

73.5 

65.6:  58.8  52.6|  47.1|         •         ! 

100 

97.4 

93.4 

87.5 

80.5 

72.7 

64,4 

56.6:  49.8  43.7i  38.2!                 ! 

90 

87.5 

83.6 

77.9 

71.0 

63.3 

54.2, 

47.61  40.8  34.8;'  29.3'         •         ' 

| 

80 

77.6 

73.8 

68.4 

61.6 

54.0 

46.1 

38.5:  31.8!  25,9:  20.6 

i 

70  67.7 

64.0 

58.7 

52.2 

44.8 

37.0 

29.5 

22.91  17.2,  12.0 

60|  57.8 

54.3 

49.1 

42.7 

35.5 

27.9 

20.5 

14.0;   83 

' 

40 

38.0 

34.7 

29.9 

23.9 

16.9 

9.6 

2.4'-3.9!                          i 

20 

15.1 

10.7 

5.0 

-1.7; 

-8.7 

-15.4!         ;         1         :         ;         '                   j 

0 

-4.5 

-8.6 

-13.9 

-20.2 

-27.0 

-33.3 

|!l;! 

; 

1              1               1 

1 

combined  is  obtainable  from  steam  tables.  For  instance,  at  60  F  the 
amount  of  this  heat  is  about  1057  Btu.  In  addition  to  this  heat  there  is 
involved  also  the  so-called  heat  of  mixing  which  is  frequently  considerable. 

Temperature-Pressure-Concentration  Relations 

Since  the  absorption  process  can  continue  only  as  long  as  there  is  a 
difference  in  vapor  pressure  between  the  absorbent  and  the  air-vapor 
mixture  and  since  at  a  given  temperature  of  the  absorbent  the  vapor 
pressure  depends  on  the  concentration  of  the  solution,  evidently  there 

TABLE  8.    DENSITY  OF  LITHIUM  CHLORIDE  SOLUTIONS 


CONCENTRATION 

MoLSLiCJPKB 

1000  GRAINS 
WATER 

TEMPERATURE  DEQ  F 

0 

50 

100 

150 

200 

250 

300 

0 

2 

1.045 

1.037 

1.026 

1.012 

4 

1.090 

1.085 

1.076 

1.064 

1.052 

6 

1.124 

1.119 

1.111 

1.100 

1.087 

8 

1.156 

1.150 

1.143 

1.132 

1.122 

10 

1,188 

1.181 

1.172 

1.162 

1.152 

1.142 

12 

1,217 

1.209 

1.199 

1.188 

1.178 

1.168 

14 

1.242 

1.235 

1.225 

1.214 

1.203 

1.192 

16 

1.257 

1.248 

1.236 

1.226 

1.215 

18 

1.279 

1.270 

1.259 

1.248 

1.237 

20 

1.291 

1.280 

1.279 

1.568 

22 

1.310 

1.289 

1.278 

1.267 

24 

1.317 

1.307 

1.296 

1.286 

26 

1.313 

1.312 

1.302 

28 

1.338 

1.327 

1.318 

30 

1.34 

1.33 

32 

1.35 

46 


CHAPTER  2.    REFRIGERANTS  AND  AIR  DRYING  AGENTS 


TABLE  9.     VISCOSITY  OF  LITHIUM  CHLORIDE  SOLUTIONS  (MILLIPOISE) 


TEMP. 
DEGF 

CONCENTRATION  IN  JM.OLAL 

0 

2 

4 

6 

8 

10 

12 

14 

16 

18 

20 

22 

24 

0 

56.75 

72.44 

97.05 

136.8 

199.5 

20 

28.91 

37.07 

47.42 

63.09 

84.94 

123.3 

178.6 

40 

15.45 

19.91 

25.53 

32.58 

43.05 

58.48 

81.10 

116.1 

165.6 

60 

11.02 

14.26 

18.37 

23.55 

30.90 

41.40 

56.62 

79.80 

111.2 

156.3 

80 

8.61 

11.19 

14.42 

18.62 

24.32 

32.28 

43.45 

60.26 

82.04 

113.8 

100 

6.82 

8.89 

11.48 

14.94 

19.36 

25.59 

33.96 

46.13 

61.52 

84.72 

118.3 

120 

5.60 

7.31 

9.51 

12.30 

15.92 

20.99 

27.67 

36.64 

48.31 

65.77 

89.95 

140 

4.70 

6.15 

8.07 

10.42 

13.43 

17.66 

22.96 

30.06 

38.99 

52.48 

71.12 

95.94 

160 

4.01 

5.25 

6.92 

8.93 

11.51 

15.00 

19.36 

25.06 

32.14 

42.76 

56.89 

75.86 

106.2 

180 

3.48 

4.56 

6.01 

7.78 

10.00 

12.91 

16.56 

21.28 

27.10 

35.48 

46.45 

60.67 

84.33 

200 

3.05 

4.01 

5.28 

6.86 

8.79 

11.22 

14.32 

18.28 

23.12 

29.92 

38.55 

50.70 

67.92 

220 

2.72 

3.58 

4.72 

6.14 

7.83 

9.93 

12.59 

16.00 

20.14 

25.64 

32.96 

43.05 

56.49 

240 

2.43 

3.21 

4.25 

5.50 

7.02 

8.83 

11.12 

14.09 

17.62 

22.18 

28.31 

36.98 

47.42 

260 

2.19 

2.90 

3.84 

4.94 

6.46 

7.91 

9.91 

12.47 

15.50 

19.36 

24.60 

31.92 

40.55 

280 

2.00 

2.66 

3.52 

4.51 

5.75 

7.19 

8.97 

11.27 

14.00 

17.22 

21.78 

28.05 

35.56 

300 

1.86 

2.48 

3.28 

4.17 

5.32 

6.67 

8.28 

10.38 

12.82 

15.70 

19.68 

25.12 

31.92 

320 

1.74 

2.32 

3.08 

3.89 

4.94 

6.19 

7.73 

9.64 

11.86 

14.45 

18.03 

22.80 

29.11 

must  be  a  relation  between  these  quantities  which  if  known  would  state 
the  limits  of  the  process.  The  relationship  would  also  depend  on  the 
absorbent  being  used,  and  would  have  to  be  determined  for  each  substance 
used  as  an  absorbent.  Fig.  2  shows  this  relationship  graphically  for 
lithium  chloride.  It  will  be  noted  that  this  chart  is  essentially  similar 
to  that  shown  in  Fig.  1  and  its  direct  usefulness  is  limited  by  much  the 
same  considerations. 

In  order  to  permit  numerical  calculations  of  air  conditioning  problems 
it  is  desirable  to  have  tables  for  use  instead  of  a  chart  like  Fig.  2,  and 
Tables  7,  8,  9  and  10  can  be  used  in  making  calculations  for  lithium 
chloride. 

TABLE  10.    PROPERTIES  OF  LITHIUM  CHLORIDE  SOLUTIONS 


CONCENTRATION 
MOLS  (42.4  GRAMS 
LiCZ  PER  1000 
GRAINS  WATER) 

PARTIAL  HEAT 
OP  MIXING  AT 
0  F  BTU  PER  LB 

TEMPERATURE  COUP. 
OP  PARTIAL  HEAT 
OP  MIXING  BTTJ  PER 

LB  PER  F 

SPECIFIC 
HEAT  AT 
70  F 

BOILING  POINT 
F 
(AT  760  MM 
EG) 

FREEZING 
POINT 

SUBSTANCE  THAT 
FIRST  SEPARATES 
Our  ON 

FREEZING 

0 

0.0 

0.0 

0.998 

212.0 

32 

Ice 

2 

2.04 

-0.014 

0.901 

215.8 

16.3 

Ice 

4 

7.24 

-0.036 

0.831 

221.5 

-5.8 

Ice 

6 

16.7 

-0.069 

0.778 

228.9 

-34.2 

Ice 

8 

31.9 

-0.109 

0.739 

238.1 

-69 

Ice 

10 

51.1 

-0.143 

0.710 

248.4 

-90 

Ice 

12 

75.7 

-0.160 

0.687 

258.8 

-40 

IAC13H& 

14 

90.8 

-0.167 

0.666 

268.9 

1 

LiCl-3HiO 

16 

124.8 

-0.176 

0.647 

277.9 

36.5 

LiCl-2H,0 

18 

145 

-0.186 

0.631 

285.8 

58.1 

LiCl-2HzO 

20 

162 

-0.194 

0.617 

293.2 

86.4 

LiCl-HzO 

22 

171 

-0.20 

0.604 

300.2 

133 

LiCl-HzO 

24 

177 

-0.20 

0.59 

307 

156 

UCl-HiO 

26 

182 

-0.21 

0.58 

313 

180 

LiCLHlO 

28 

191 

-0.21 

0.575 

318 

190 

LiCl-HzO 

30 

194 

-0.21 

0.57 

323 

195 

UClr-H£> 

32 

198 

-0.22 

0.56 

328 

280 

LiCl   . 

47 


HEATING  VENTILATING  AIR  CONDITIONING  GUIDE  1938 


Instead  of  tabulating  the  vapor  pressure  of  the  solution  of  lithium 

chloride  it ?s  SefaSSto  tabulate  the  dew-point  of  air  m  equilibrium 

Sth  lithium  Sloridc,  since  it  is  easy  to  interpolate  between  values  of 

the  dew ££t  and  not  so  easy  to  interpolate  accurately  between  values  of 

apo pSre     The  valuesfor  dew-point  may  be  converted  to  vapor 


CONCENTRATION,  PER  CENT 
30  40  50 


1000 


500- 


M1XTURE5  OF 
SOLUTION  AND  LiCI-H2O 


MIXTURES    OF  SOLUTION  AND 
LiCl  -2H20 


MIXTURES   OF  SOLUTION    AND 
LiCI-3H20 


0.1 


FIG. 


10  15  20  25 

CONCENTRATION,     MOLAL 

2.    TEMPERATURE — PRESSURE — CONCENTRATIONS  FOR  LITHIUM  CHLORIDE 


pressures,  relative  humidity,  and  wet-bulb  of  air  in  equilibrium  by  means 
of  the  usual  psychrometric  chart  or  formula. 

In  Tables  7,  8,  9  and  10  the  unit  of  concentration  is  the  mol  A  'M' 
molal  solution  is  denned  as  a  solution  containing  M  X  42.37  grains  of 
anhydrous  lithium  chloride  per  1000  grains  of  water.  The  formula  con- 
necting concentration  in  mols  with  weight  in  per  cent  is  equivalent  to: 
[100  X  M  X  42.37]  -r  [1000  +  (M  X  42.37)]. 

48 


CHAPTER  2.   REFRIGERANTS  AND  AIR  DRYING  AGENTS 


PROBLEMS  IN  PRACTICE 

1  •  What  is  the  heat  content  above  —  40  F  of  2.5  Ib  of  ammonia  when  under  a 
pressure  of  92.9  Ih  per  square  inch  gage  and  a  temperature  of  160  F? 

First  determine  the  condition  of  the  ammonia  at  the  stated  temperature  and  pressure. 
Do  this  by  finding  the  absolute  pressure  which  in  this  case  is  92.9  Ib  gage  plus  14.7  or 
107.6  Ib  per  square  inch  absolute.  From  Table  1  note  that  the  saturation  temperature 
at  this  pressure  is  60  F.  Therefore,  the  ammonia  is  superheated  100  F,  and  the  total  heat 
per  pound  can  be  read  directly  from  the  Table  as  689.9  Btu.  In  the  2.5  Ib  of  ammonia 
there  are  2.5  X  689.9,  or  1724.75  Btu. 

2  •  "What  volume  is  necessary  to  accommodate  0.27  Ib  of  saturated  Fi2  vapor 
when  compressed  to  99.6  Ib  gage? 

The  absolute  pressure  is  99.6  plus  14.7  or  114.3  Ib.  In  Table  3  find  that  one  pound  of 
Fi2  vapor  saturated  occupies  0.368  cu  ft.  Then  the  0.27  Ib  would  occupy  0.27  X  0.368, 
or  0.099  cu  ft. 

3  •  How  much  heat  would  be  removed  from  air  passing  over  a  coil  through 
which  2  Ib  of  methyl  chloride  per  minute  is  forced?    The  coil  is  under  a  gage 
pressure  of  64  Ib  per  square  inch  and  the  liquid  refrigerant  is  completely  vapor- 
ized in  passing  through  the  coil. 

Find  that  the  absolute  pressure  is  64  plus  14.7  or  78.7  Ib  per  sq  in.  From  Table  4  note 
that  the  saturation  temperature  at  this  pressure  is  75  F  (nearly)  and  that  the  heat 
content  per  pound  of  the  vapor  is  207.8  Btu.  Also  that  the  heat  content  of  the  liquid  is 
42.2  Btu  per  pound.  Subtract  42.2  from  207.8  and  165.6  Btu  per  pound  is  the  heat 
necessary  to  change  the  liquid  refrigerant  to  a  vapor  (latent  heat).  As  the  heat  to 
accomplish  this  change  comes  from  the  air  around  the  coil,  the  heat  removed  from  the 
air  is  165.6  Btu  per  pound  of  methyl  chloride  evaporated  in  the  coil.  When  the  refriger- 
ant is  circulated  at  2  Ib  per  minute,  2  X  165.6,  or  331.2  Btu  per  minute  are  removed  from 
the  air,  or  refrigerating  effect  is  produced  at  the  rate  of  331.2  -5-  200,  or  1.65  tons. 

4  •  Calculate  the  dew-point,  wet-bulb,  relative  humidity  and  absolute  hu- 
midity of  air  in  equilibrium  at  100  F  with  pure  lithium  chloride  solution  of 
density  1.270. 

From  Table  8  the  concentration  of  a  solution  of  density  1.270  at  100  F  is  18.0  M.  From 
Table  7  the  dew-point  of  18  M  lithium  chloride  at  100  F  is  43.7  F.  From  Table  6, 
Chapter  1,  the  partial  pressure  of  water  over  the  solution  is  0.2858  in.  of  Hg,  the  absolute 
humidity  is  42.00  grains  per  pound  dry  air,  and  the  wet-bulb  is  65.8  F.  The  relative 
humidity  is  14.0  per  cent. 

5  •  Calculate  the  boiling  point,  and  freezing  point  of  18  M  lithium  chloride 
solutions. 

From  Table  10,  boiling  point  (standard)  is  285.8  F,  freezing  point  is  58.1  F.  The  salt 
precipitated  on  cooling  to  this  temperature  has  the  composition  LiCl-2H20. 

6  •  Calculate  the  heat  of  vaporization  of  1  Ib  of  water  from  a  large  amount  of 
lithium  chloride  solution  at  the  boiling  point. 

The  heat  of  boiling  is  equal  to  the  heat  of  mixing  plus  the  heat  of  boiling  pure  water  at 
the  same  temperature.  The  heat  of  mixing  from  Table  10  at  18  M  and  285.8  F  is  (145 
—  0.186  X  285.8)  =  92  Btu  per  pound.  The  heat  of  vaporization  of  water  from  steam 
tables  at  285.8  F  is  920  Btu  per  pound.  Therefore  the  heat  of  vaporization  of  water 
from  the  solution  is  920  -f  92  =  1012  Btu  per  pound. 

7  •  One  thousand  pounds  of  air  per  minute  at  100  F  dry -bulb  with  a  dew-point 
of  70  F  and  a  relative  humidity  of  39  per  cent  is  passed  over  18  M  lithium  chloride 
solution.    The  rate  of  flow  of  the  solution  is  200  gpm  and  the  entering  tempera- 
ture is  80  F.    The  air  leaves  the  absorber  at  85  F  dry-bulb  and  dew-point  of 
35  F.    Calculate  (a)  the  heat  to  be  removed  from  the  lithium  chloride  solution 

49 


HEATING  VENTILATING  AIR  CONDITIONING  GUIDE  1938 


to  maintain  these  conditions,  and  (6)  the  temperature  rise  of  the  solution  in 
passing  through  the  absorber. 

a.  The  heat  content  of  the  entering  air:  From  Table  6,  Chapter  1,  weight  of  vapor  at 
70  F  dew-point  is  0.01574  ib  times  heat  content  of  steam  at  100  F  dry-bulb  is  1104.2 
(Table  8,  Chapter  1)  equals  17.41  Btu  per  pound  plus  heat  content  of  dry  air  at  100  F 
is  24.0  (Table  6,  Chapter  1)  resulting  in  heat  content  of  mixture  as  41.41  Btu  per  pound. 

Similarly,  the  heat  content  of  the  leaving  air:  Weight  of  vapor  at  35  F  dew-point  is 
0.004262  X  1097.5  «  4.68  Btu  per  pound  plus  heat  content  of  dry  air  at  85  F  is  20.39 
resulting  in  heat  content  of  mixture  as  25.07  Btu  per  pound. 

Heat  to  be  extracted  from  air  is  1000  X  (41.41  -  25.07)  =  16,340  Btu  per  minute. 
Add  to  this  the  heat  of  mixing  of  18M  lithium  chloride  at  80  F  equals  145  -  (0.186  X 
80)  =  130  Btu  per  pound  (Table  10)  or  for  1000  Ib  of  air  X  (0,01574  -  0.00426)  X  130  = 
1494  Btu  per  minute.  Heat  to  be  removed  from  solution  is  16,340  +  1494  =  17,834 
Btu  per  minute. 

6.  The  weight  of  solution  circulated  is  200  X  1.275  (Table  8)  X  8.33  =  2124  Ib  per 
minute.  Its  heat  capacity  is  2124  X  0.631  (Table  10)  =  1340  Btu  per  minute  per  degree 
Fahrenheit.  The  temperature  rise  is  17,834  •*•  1340  =  13.31  F. 


Chapter  3 

PHYSICAL  AND  PHYSIOLOGICAL  PRINCIPLES 
OF  AIR  CONDITIONING 

Vitiation  of  Air,  Heat  Regulation  in  Man,  Effects  of  Heat, 
Effects  of  Cold  and  Temperature  Changes,  Acclimatization, 
Effective  Temperature  Index  of  Warmth,  Optimum  Air  Condi- 
tions, Winter  and  Summer  Comfort  Zone,  Optimum  Humid- 
ity, Air  Quality  and  Quantity,  Air  Movement  and  Distribution, 
Natural  and  Mechanical  Ventilation,  Heat  and  Moisture 
Losses,  Ultra- Violet  Radiation  and  lonization,  Recirculation 
and  Ozone,  Ventilation  Standards 

VENTILATION  is  defined  in  part  as  "  the  process  of  supplying  or 
removing  air  by  natural  or  mechanical  means  to  or  from  any  space." 
(See  Chapter  45,)  The  word  in  itself  implies  quantity  but  not  necessarily 
quality.  ^  From  the  standpoint  of  comfort  and  health,  however,  the 
problem  is  now  considered  to  be  one  of  securing  air  of  the  proper  quality 
rather  than  of  supplying  a  given  quantity. 

The  term  air  conditioning  in  its  broadest  sense  implies  control  of  any  or 
all  of  the  physical  or  chemical  qualities  of  the  air.  More  particularly,  it 
includes  the  simultaneous  control  of  temperature,  humidity,  movement, 
and  purity  of  the  air.  The  term  is  broad  enough  to  embrace  whatever 
other  additional  factors  may  be  found  desirable  for  maintaining  the 
atmosphere^of  occupied  spaces  at  a  condition  best  suited  to  the  physio- 
logical requirements  of  the  human  body. 

VITIATION  OF  AIR 

Under  the  artificial  conditions  of  indoor  life,  the  air  undergoes  certain 
physical  and  chemical  changes  which  are  brought  about  by  the  occupants 
themselves.  The  oxygen  content  is  somewhat  reduced,  and  the  carbon 
dioxide  slightly  increased  by  the  respiratory  processes.  Organic  matter, 
which  is  usually  perceived  as  odors,  comes  from  the  nose,  mouth,  skin 
and  clothing.  The  temperature  of  the  air  is  increased  by  the  metabolic 
processes,  and  the  humidity  raised  by  the  moisture  emitted  from  the  skin 
and  lungs.  There  is  also  a  marked  decrease  in  both  positive  and  negative 
ions  in  the  air  of  occupied  rooms  but  the  significance  of  this  factor  is 
still  questionable1. 

Contrary  to  old  theories,  the  usual  changes  in  oxygen  and  carbon 
dioxide  are  of  no  physiological  concern  because  they  are  much  too  small 
even  under  the  worst  conditions.  The  amount  of  carbon  dioxide  in  air  is 

Changes  in  Ionic  Content  in  Occupied  Rooms  Ventilated,  by  Natural  and  MechanicalTMethods  by 
C.  P.  Yaglou,  L.  C.  Benjamin  and  S.  P.  Choate  (A.S.H.V.E.  TRANSACTIONS,  Vol.  38, 1932,  p.  191). 

51 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 

often  used  in  ventilation  work  as  an  index  of  odors  of  human  origin,  but 
the  information  it  affords  rarely  justifies  the  labor  involved  in  making  the 
observation2- 3.  Little  is  known  of  the  identity  and  physiological  effects  of 
the  organic  matter  given  off  in  the  process  of  respiration.  The  former 
belief  that  the  discomfort  experienced  in  confined  spaces  was  due  to  some 
toxic  volatile  matter  in  the  expired  air  is  now  limited,  in  the  light  of 
numerous  researches,  to  the  much  less  dogmatic  view  that  the  presence  of 
such  a  substance  has  not  been  demonstrated.  The  only  certain  fact  is 
that  expired  and  transpired  air  is  odorous  and  offensive,  and  it  is  capable 
of  producing  loss  of  appetite  and  a  disinclination  for  physical  activity. 
These  reasons,  whether  esthetic  or  physiological,  call  for  the  introduction 
of  a  certain  minimum  amount  of  clean  outdoor  air  to  dilute  the  odoriferous 
matter  to  a  concentration  which  is  not  objectionable. 

A  certain  part  of  the  dissemination  of  disease  in  confined  spaces  is 
caused  by  the  emission  of  pathogenic  bacteria  from  infected  persons. 
Droplets  sprayed  into  the  air  in  talking,  coughing,  sneezing,  etc.,  do  not 
all  fall  immediately  to  the  ground  within  a  few  feet  from  the  source,  as  it 
was  formerly  believed.  The  large  droplets  do,  of  course,  but  minute 
droplets  less  than  0.1  mm.  in  diameter  evaporate  to  dryness  before  the}' 
fall  the  height  of  a  man.  Nuclear  residues  from  such  sources,  which  may 
contain  infective  organisms  drift  long  distances  with  the  air  currents  and 
the  virus  may  remain  alive  long  enough  to  be  transmitted  to  other  persons 
in  the  same  room  or  building.  Wells4  recovered  droplet  nuclei  from 
cultures  of  resistant  micro-organisms  a  week  after  inoculation  into  a 
tight  chamber  of  300  cu  ft  capacity.  Typical  organisms  of  infections  of 
the  upper  respiratory  tract  (pneumococcus  type  I,  B.  diphtheriae,  Strep- 
tococcus hemolyticus,  and  Streptococcus  viridans)  were  found  to  die 
out  quite  soon  when  exposed  to  light  and  air,  and  could  be  recovered  from 
the  air  in  small  numbers  only  48  hours  after  inoculation/  Organisms 
typical  of  the  intestinal  tract  (B.  coli,  B.  typhosus,  B.  paratyphosus, 
A.  and  B.  dysenteriae)  were  not  recovered  12  hours  after  inoculation. 

The  significant  factors  in  infection  are  believed  to  be  the  numbers,  of 
infective  organisms  encountered,  the  frequency  of  exposure,  and  the 
resistance  of  the  individual  including  the  degree  of  acquired  immunity. 
The  probability  of  encountering  a  sufficient  number  of  organisms  to 
break  down  the  natural  body  defense  is  related  to  the  air  space  per  person 
and  the  quantity  of  clean  air  supplied.  Except  in  badly  ventilated  rooms, 
the  danger  is  believed  to  be  "much  contracted  in  space,  limited  in  time 
and  restricted  to  comparatively  few  diseases."5 

^  Practical  possibilities  in  sterilizing  air  supplies  by  the  use  of  ultra- 
violet light  are  now  being  studied6. 

The  primary  factors  in  air  conditioning  work,  in  the  absence  of  any 
specific  contaminating  source,  are  temperature,  radiation,  drafts  and 

TRAJ?sSo^AVolC1^9nS19Sd  AiJ6?{8triblltion'  by  R  C  Houghten  and  J.  L.  Blackshaw  (A.S.H.V.E. 
v  inleontiiQ7An  RW\rements,  *>y  c-  p-  Yaglou,  E.  C.  Riley  and  D.  I.  Coggins  (A.S.H.V.E.  TRANSACTIONS, 

vol.  <U,   laoO,  p.   L63). 

oi^"*001* Infection  and  Sanitary  Air  Control,  by  W.  F.  Wells,  (Journal  Industrial  Hygiene,  November, 

oOj. 

B^TcSiVN1l?Ui9&fnd  Hygiene'  by  Muton  J-  Rosenau  (6th  edition,  pp.  909-917,  D.  Appleton- 
slTsa^^gO)2'  ^OU  Exp°Sed  t0  UttxBrVtolet  Radiation  in  Air.  by  W.  F.  Wells,  and  G.  M.  Fair  (Science, 

52 


CHAPTER  3.   PHYSICAL  &  PHYSIOLOGICAL  PRINCIPLES  OF  AIR  CONDITIONING 


body  odors.     As  compared  with  these  physical  factors,  the  chemical 
factors  are,  as  a  general  rule,  of  secondary  importance. 

HEAT  REGULATION  IN  MAN 

The  importance  of  the  thermal  factors  arises  from  the  profound  in- 
fluence which  they  exert  upon  body  temperature,  comfort  and  health. 
Body  temperature  depends  on  the  balance  between  heat  production  and 
heat  loss.  The  heat  resulting  from  the  combustion  of  food  within  the 
body  maintains  the  body  temperature  well  above  that  of  the  surrounding 
air.  At  the  same  time,  heat  is  constantly  lost  from  the  body  by  radiation, 
conduction  and  evaporation.  Since,  under  ordinary  conditions,  the  body 
temperature  is  maintained  at  its  normal  level  of  about  98.6  F,  the  heat 
production  must  be  balanced  by  the  heat  loss.  In  healthy  persons  this 
takes  place  automatically  by  the  action  of  the  heat  regulating  mechanism. 

According  to  the  general  view,  special  areas  in  the  skin  are  sensitive  to 
heat  and  cold.  Nerve  courses  carry  the  sense  impressions  to  the  brain  and 
the  response  comes  back  over  another  set  of  nerves,  the  motor  nerves,  to 
the  musculature  and  to  all  the  active  tissues  in  the  body,  including  the 
endocrine  glands.  In  this  way,  a  two-sided  mechanism  controls  the  body 
temperature  by  (1)  regulation  of  internal  heat  production  (chemical 
regulation) ,  and  (2)  regulation  of  heat  loss  by  means  of  automatic  varia- 
tion in  the  rate  of  cutaneous  circulation  and  the  operation  of  the  sweat 
glands  (physical  regulation).  The  mechanisms  of  adjustment  are  complex 
and  little  understood  at  the  present  time.  Coordination  of  these  dif- 
ferent mechanisms  seems  to  vary  greatly  with  different  air  conditions. 

With  rising  air  temperatures  up  to  75  F  or  80  F,  metabolism,  or  internal 
heat  production,  decreases  slightly7,  probably  by  an  inhibitory  action  on 
heat  producing  organs,  especially  the  adrenal  glands,  which  seem  to  exert 
the  major  influence  on  basic  combustion  processes  in  the  body.  The  blood 
capillaries  in  the  skin  become  dilated  by  reflex  action  of  the  vasomotor 
nerves,  allowing  more  blood  to  flow  into  the  skin,  and  thus  increase  its 
temperature  and  consequently  its  heat  loss.  The  increase  in  peripheral 
circulation  is  at  the  expense  of  the  internal  organs.  If  this  method  of 
cooling  is  not  in  itself  sufficient,  the  stimulus  is  extended  to  the  sweat 
glands  which  allow  water  to  pass  through  the  surface  of  the  skin,  where  it 
is  evaporated.  This  method  of  cooling  is  the  most  effective  of  all,  as  long 
as  the  humidity  of  the  air  is  sufficiently  low  to  allow  for  evaporation.  In 
high  humidities,  where  the  difference  between  the  dew-point  temperature 
of  the  air  and  body  temperature  is  not  sufficient  to  allow  rapid  evapora- 
tion, equally  good  results  may  be  obtained  by  increasing  the  air  move- 
ment, and  hence  the  heat  loss  by  conduction  and  evaporation. 

In  cold  environments,  in  order  to  keep  the  body  warm  there  is  an  actual 
increase  in  metabolism  brought  about  partly  by  voluntary  muscular  con- 
tractions (shivering)  and  partly  by  an  involuntary  reflex  upon  the  heat 
producing  organs.  The  surface  blood  vessels  become  constricted,  and 
the  blood  supply  to  the  skin  is  curtailed  by  vasomotor  shifts  to  the  internal 
organs  in  order  to  conserve  body  heat.  The  sweat  glands  become  inactive. 


7Heat  and  Moisture  Losses  from  the  Human  Body  and  Their  Relation  to  Air  Conditioning  Problems, 
by  F.  C.  Houghten,  W.  W.  Teague,  W.  E.  Miller  and  W.  P.  Yant  (A.S.H.V.E.  TRANSACTIONS,  Vol.  35, 
1929,  p.  245). 

53 


HEATING   VENTILATING  AIR  CONDITIONING  GUIDE  1938 


EFFECTS  OF  HEAT 

Although  the  human  organism  is  capable  of  adapting  itself  to  variations 
in  environmental  conditions,  its  ability  to  maintain  heat  equilibrium  is 
limited.  The  upper  limit  of  effective  temperature  to  which  the  human 
organism  is  capable  of  adapting  itself  without  serious  discomfort  or 
injury  to  health  is  90  deg  ET  for  men  at  rest  and  between  80  and  90  deg 
ET  for  men  at  work  depending  upon  the  rate  of  work.  Within  these 
limits  a  new  equilibrium  is  established  at  a  higher  body  temperature  level 
through  a  chain  of  physiological  adjustments.  The  heat  regulating  center 
fails,  when  the  external  temperature  is  so  abnormally  high  that  bodily 
heat  cannot  be  eliminated  as  fast  as  it  is  produced.  Part  of  it  is  retained 
in  the  body,  causing  a  rise  in  skin  and  deep  tissue  temperature,  an  increase 
in  the  heart  rate,  and  accelerated  respiration.  (See  Table  1.)  In  extreme 

TABLE  1.    PHYSIOLOGICAL  RESPONSES  TO  HEAT  OF  MEN  AT  REST  AND  AT  WORK* 


MEN  AT  WOBK 

ACTUAL 

MEN  AT  RBST 

90,000  FT-LB  of  WORK  PER  HOUE 

EfTccxtni 
TBJCP. 

TEMP. 
IDio 
FAHR) 

Rise  in 
Rectal 
Temp. 

Fahrper 
Hour) 

Increase 
in  Pulse 
Rate 
(gate  per 
Min  per 
Hour) 

Loss  in  Body 
Weight  by 
Perspiration 
(Lb  perHr) 

Total  Work 
Accomplished 
(Ft-Lb) 

Rise  in 
Body  Temp. 
(Deg  Fair 
per  Hr) 

Increase  in 
Pulse  Rate 
(Beat*  per 
Min  per  Hr) 

Approximate 
Loss  in  Body 
Wt.  by  Per- 
spiration (Lb 
per  Hr) 

60 



225,000 

0.0 

6 

0.5 

70 

o.o 

6 

6.2~ 

225,000 

0.1 

7 

0.6 

80 

96.1 

0.0 

0 

0.3 

209,000 

0.3 

11 

0.8 

85 

96.6 

0.1 

i 

0.4 

190,000 

0.6 

17 

1.1 

90 

97.0 

0.3 

4 

0.5 

153,000 

1.2 

31 

1.5 

95 

97.6 

0.9 

15 

0.9 

102,000 

2.3 

61 

2.0 

100 

99.6 

2.2 

40 

1.7 

67,000 

4.0 

103b 

2.7 

105 

104.7 

4.0 

83 

2.7 

49,000 

6.0*> 

158b 

3.5*> 

110 



5.9b 

137b 

4.0*> 

37,000 

8.5b 

237* 

4.4b 

•Data  by  A.S.H.V.E.  Research  Laboratory. 

bCompnted  va!ue  from  exposures  lasting  less  than  one  hour. 

heat,  the  metabolic  rate  is  markedly  increased  owing  to  the  excessive  rise 
in  body  temperature8,  and  a  vicious  cycle  results  which  may  eventually 
lead  to  serious  physiologic  damage. 

Examples  of  this  are  met  with  in  unusually  hot  summer  weather  and  in 
hot  industries  where  the  radiant  heat  from  hot  objects  renders  heat  loss 
from  the  body  by  radiation  and  convection  impossible.  Consequently, 
the  workers  depend  entirely  on  evaporation  for  the  elimination  of  body 
heat.  They  stream  with  perspiration  and  drink  liquids  abundantly  to 
replace  the  loss. 

One  of  the  deleterious  effects  of  high  temperatures  is  that  the  blood  is 
diverted  from  the  internal  organs  to  the  surface  capillaries,  in  order  to 
serve  in  the  process  of  cooling.  This  affects  the  stomach,  heart,  lungs  and 
other  vital  organs,  and  it  is  suggested  that  the  feeling  of  lassitude  and 
discomfort  experienced  is  due  in  part  to  the  anaemic  condition  of  the  brain 
The  stomach  loses  some  of  its  power  to  act  upon  the  food,  owing  to  a 


54 


CHAPTER  3.   PHYSICAL  &  PHYSIOLOGICAL  PRINCIPLES  OF  AIR  CONDITIONING 

diminished  secretion  of  gastric  juice,  and  there  is  a  corresponding  loss  in 
the  antiseptic  and  antifermentive  action  which  favors  the  growth  of 
bacteria  in  the  intestinal  tract9.  These  are  considered  to  be  the  potent 
factors  in  the  increased  susceptibility  to  gastro-intestinal  disorders  in  hot 
summer  weather.  The  victim  may  lose  appetite  and  suffer  from  indiges- 
tion, headache  and  general  enervation,  which  may  eventually  lead  to  a 
premature  old  age. 

In  warm  atmospheres,  particularly  during  physical  work,  a  considerable 
amount  of  chloride  is  lost  from  the  system  through  sweating.  The  loss  of 
this  substance  may  lead  to  attacks  of  cramps,  unless  the  salts  are  replaced 
in  the  drinking  water.  In  order  to  relieve  both  cramps  and  fatigue, 
Moss10  recommends  the  addition  of  6  grams  of  sodium  chloride  and  4  grams 
of  potassium  chloride  to  a  gallon  of  water. 

The  deleterious  physiologic  effects  of  high  temperatures  exert  a  power- 
ful influence  upon  physical  activity,  accidents,  sickness  and  mortality. 
Both  laboratory  and  field  data  show  clearly  that  physical  work  in  warm 
atmospheres  is  a  great  effort,  and  that  production  falls  progressively  as 
the  temperature  rises.  The  incidence  of  industrial  accidents  reaches  a 
minimum  at  about  68  F,  increasing  above  and  below  that  temperature. 
Sickness  and  mortality  rates  increase  progressively  as  the  temperature 
rises. 

EFFECTS  OF  COLD  AND  TEMPERATURE  CHANGES 

The  action  of  cold  on  human  beings  is  not  well  known.  Cold  affects  the 
human  organism  in  two  ways:  (1)  through  its  action  on  the  body  as  a 
whole,  and  (2)  through  its  action  on  the  mucous  membranes  of  the  upper 
respiratory  tract.  Little  exact  information  is  available  on  the  latter. 

On  exposure  to  coldr  the  loss  of  heat  is  increased  considerably  and  only 
within  certain  limits  is  compensation  possible  by  increased  heat  produc- 
tion and  decreased  peripheral  circulation.  The  rectal  temperature  often 
rises  upon  exposure  to  cold  but  the  pulse  rate  and  skin  temperature  fall. 
The  blood  pressure  increases,  owing  to  constriction  in  the  peripheral 
vessels.  Just  how  cold  affects  health  is  not  well  understood.  It  imposes 
an  extra  load  upon  the  heat-producing  organs  to  maintain  body  tempera- 
ture. The  strain  falls  largely  upon  digestion,  metabolism,  blood  circu- 
lation, and  the  kidneys,  and  indirectly  upon  the  nervous  system11. 

Although  the  seasonal  increase  in  morbidity  and  mortality  sets  in  with 
the  approach  of  cold  weather  and  subsides  in  the  warm  summer  months, 
little  is  known  of  the  specific  causative  factors  and  their  mechanism  of 
action.  Over-crowding  of  buildings,  overheated  rooms,  lack  of  venti- 
lation, and  close  personal  contacts  are  frequently  held  responsible  for  our 
winter  ills,  but  the  evidence  is  not  conclusive. 

In  extremely  cold  atmospheres  compensation  by  increased  metabolism 
becomes  inadequate.  The  body  temperature  falls  and  the  reflex  irritability 
of  the  spinal  cord  is  markedly  affected.  The  organism  may  finally  pass 
into  an  unconscious  state  which  ends  in  death. 

•innueucc  of  Effective  Temperature  upon  Bactericidal  Action  of  Gastro-intestinal  Tract,  by  Arnold  and 
Brody  (Proceedings  Society  Exp.  Biol.  Mcd.  Vol.  24, 1927,  p.  832). 

10Some  Effects  of  High  Air  Temperatures  upon  the  Miner,  by  K.  N.  Moss  (.Transactions  Institute  of 
Mining  Engineers,  Vol.  66,  1924,  p.  284). 
"Loc.  Cit.  Note  5. 

55 


HEATING   VENTIIATING   AIR  CONDITIONING   GUIDE  1938 

Cannon  showed  that  excessive  loss  of  heat  is  associated  with  increased 
activity  of  the  adrenal  medulla12.  The  extra  output  of  adrenin  hastens 
heat  production  which  protects  the  organism  against  cooling.  Bast13 
found  a  degeneration  of  thyroid  and  adrenal  glands  upon  exposure  to  cold. 

A  moderate  amount  of  variability  in  temperature  is  known  to  be 
beneficial  to  health,  comfort,  and  the  performance  of  physical  and  mental 
work.  On  the  other  hand,  extreme  changes  in  temperature,  such  as  those 
experienced  in  passing  from  a  warm  room  to  the  cold  air  out-of-doors, 
appear  to  be  harmful  to  the  tissues  of  the  nose  and  throat  which  are  the 
portals  for  the  entry  of  respiratory  diseases. 

Experiments  show  that  chilling  causes  a  constriction  of  the  blood 
vessels  of  the  palate,  tonsils,  throat,  and  nasal  mucosa,  which  is  accom- 
panied by  a  fall  in  the  temperature  of  the  tissues.  On  re-warming,  the 
palate  and  throat  do  not  always  regain  their  normal  temperature  and 
blood  supply.  This  anaemic  condition  favors  bacterial  activity  and  it 
probably  plays  a  part  in  the  disposition  of  common  cold  and  other 
respiratory  diseases.  It  is  believed  that  the  lowered  resistance  is  due  to  a 
diminution  in  the  number  and  phagocytic  activity  of  the  leucocytes 
(white  blood  cells)  brought  about  by  exposure  to  cold  and  by  changes 
in  temperature. 

Sickness  records  in  industries  seem  to  strengthen  this  belief.  The 
Industrial  Fatigue  Research  Board  of  En'gland14  found  that  in  workers 
exposed  to  high  temperatures  and  to  changes  in  temperature,  namely, 
steel  melters,  puddlers,  and  general  laborers,  there  is  an  excess  of  all 
sickness,  the  excess  among  the  puddlers  being  due  chiefly  to  respiratory 
diseases  and  rheumatism.  The  causative  factor  was  not  the  heat  itself 
but  the  sudden  changes  in  temperature  to  which  the  workers  were  exposed. 
The  tin-plate  millmen  who  were  not  exposed  to  chills,  since  they  work 
almost  continuously  throughout  the  shift,  had  no  excess  of  rheumatism 
and  respiratory  diseases.  On  the  other  hand,  the  blast-furnacemen,  who 
work  mostly  in  the  open,  showed  more  respiratory  sickness  than  the  steel 
workers.  This  experience  in  British  factories  is  well  in  accord  with  the 
findings  in  American  industries15-  16.  According  to  these  data  the  highest 
pneumonia  death  rate  is  associated  with  dust,  extreme  heat,  exposure  to 
cold,  and  to  sudden  changes  in  temperature. 

ACCLIMATIZATION 

Acclimatization  and  the  factor  of  psychology  are  two  important  in- 
fluences in  air  conditioning  which  cannot  be  ignored.  The  first  is  man's 
ability  to  adapt  himself  to  changes  in  air  conditions;  the  second  is  an 
intangible  matter  of  habit  and  suggestion. 

Some  persons  regard  the  unnecessary  endurance  of  cold  as  a  virtue. 


^  f.  Cannon,  A.  Guerido,  S.  W.  Britten 

-  Bast*  j-  s-  Supernaw'  B-  Lieberman  and  j-  Munr° 

Lolhdeon)°n  ^  Sted  Industry'  by  H'  M'  Vernon  industrial  Fatigue  Research 

telWfarf  Bulletin, 
Bloomfield< 


56 


CHAPTER  3.   PHYSICAL  &  PHYSIOLOGICAL  PRINCIPLES  OF  AIR  CONDITIONING 

They  believe  that  the  human  organism  can  adapt  itself  to  a  wide  range  of 
air  conditions  with  no  apparent  discomfort  or  injury  to  health.  In  the 
light  of  the  present  knowledge  of  air  conditioning  these  views  are  not 
justified.  Acclimatization  to  extreme  conditions  involves  a  strain  upon 
the  heat  regulating  system  and  it  interferes  with  the  normal  physiologic 
functions  of  the  human  body.  Thousands  of  years  in  the  heat  of  Africa 
do  not  seem  to  have  acclimatized  the  Negro  to  a  temperature  averaging 
80  F.  The  same  holds  true  of  northern  races  with  respect  to  cold,  although 
the  effects  are  mitigated  by  artificial  control.  All  this  seems  to  indicate 
that  adaptation  to  an  environment  averaging  between  60  and  80  F  is  a 
very  primitive  trait17. 

Within  these  limits,  however,  there  does  occur  a  definite  adaptation  to 
external  temperature  level.  People  and  animals  raised  under  conditions 
of  tropical  moist  heat  have  a  lower  rate  of  heat  production  than  do  those 
who  grow  up  in  cooler  environments.  This  causes  them  to  stand  chilling 
poorly  as  they  are  unable  to  quickly  increase  internal  combustion  to  keep 
up  the  body  temperature.  For  this  reason  they  have  trouble  standing 
the  cold,  stormy  weather  of  the  temperate  zones,  and  when  exposed  to  it 
are  very  susceptible  to  respiratory  infections.  Likewise,  people  living  in 
cool  climates  suffer  greatly  in  the  moist  heat  of  the  tropics  until  their 
adrenal  activity  has  slowed  down.  Within  a  couple  of  years,  however, 
they  find  themselves  standing  the  heat  much  better  and  disliking  cold. 
They  become  acclimated  by  a  definite  change  in  the  combustion  level 
within  the  body18. 

In  certain  individuals  the  psychologic  factor  is  more  powerful  than 
acclimatization.  A  fresh  air  fiend  may  suffer  in  a  room  with  windows 
closed  regardless  of  the  quality  of  the  air.  As  a  matter  of  fact,  instances 
are  known  in  which  paid  subjects  refused  to  stay  in  a  windowless  but 
properly  conditioned  experimental  chamber  because  the  atmosphere  felt 
suffocating  to  them  upon  entering  the  room. 

EFFECTIVE  TEMPERATURE  INDEX  OF  WARMTH 

Sensations  of  warmth  or  cold  depend,  not  only  on  the  temperature  of 
the  surrounding  air  as  registered  by  a  dry-bulb  thermometer,  but  also 
upon  the  temperature  indicated  by  a  wet-bulb  thermometer.  Dry  air  at 
a  relatively  high  temperature  may  feel  cooler  than  air  of  considerably 
lower  temperature  with  a  high  moisture  content.  Air  motion  makes  any 
moderate  condition  feel  cooler. 

On  the  other  hand,  in  cold  environments  an  increase  in  humidity 
produces  a  cooler  sensation.  The  dividing  line  at  which  humidity  has  no 
effect  upon  warmth  varies  with  the  air  velocity  and  is  about  46  F  (dry- 
bulb)  for  still  air  and  about  51,  56  and  59  F  for  air  velocities  of  100,  300 
and  500  fpm,  respectively.  Radiation  from  cold  or  warm  surfaces  is 
another  important  factor  under  certain  conditions. 

Combinations  of  temperature,  humidity  and  air  movement  which 
induce  the  same  feeling  of  warmth  are  called  thermo-equivalent  con- 


"Civilization  and  Climate,  by  Ellsworth  Huntington,  Yale  University  Press,  1924. 
"Air  Conditioning  in  its  Relation  to  Human  Welfare,  by  C.  A.  Mills  (A.S.H.V.E.  TRANSACTIONS,  Vol. 
40,  1934,  p.  289). 

57 


HEATING  VENTILATING  AIR  CONDITIONING   GUIDE  1938 


I     jj 


-50 


FIG.  1.    EFFECTIVE  TEMPERATURE  CHART  SHOWING  NORMAL  SCALE  OF  EFFECTIVE 

TEMPERATURE.    APPLICABLE  TO  INHABITANTS  OF  THE  UNITED  STATES  UNDER 

FOLLOWING  CONDITIONS: 


i/***  c.ustomary  indoor  clothing.    B.  Activity:  Sedentary  or  light  muscular  work.    C.  Heating 
Methods:  Convection  type.  i.e.  warm  air,  direct  steam  or  hot  water  radiators,  plenum  systems.        amnn* 

58 


CHAPTER  3.    PHYSICAL  &  PHYSIOLOGICAL  PRINCIPLES  OF  AIR  CONDITIONING 

ditions.  A  series  of  tests19-  20»  «•  22  at  the  A.S.H.V.E.  Research  Labora- 
tory, Pittsburgh,  established  the  equivalent  conditions  met  with  in 
general  air  conditioning  work.  This  scale  of  thermo-equivalent  conditions 
not  only  indicates  the  sensation  of  warmth,  but  also  determines  the 
physiological  effects  on  the  body  induced  by  heat  or  cold.  For  this  reason, 
it  is  called  the  effective  temperature  scale  or  index. 

Effective  temperature  is  an  empirically  determined  index  of  the  degree 
of  warmth  perceived^  on  exposure  to  different  combinations  of  tempera- 
ture, humidity,  and  air  movement.  It  was  determined  by  trained  subjects 
who  compared  the  relative  warmth  of  various  air  conditions  in  two  ad- 
joining conditioned  rooms  by  passing  back  and  forth  from  one  room  to 
the  other. 

Effective  temperature  is  not  in  itself  an  index  of  comfort,  except  under 
ordinary  humidity  conditions  (30  to  60  per  cent)  when  the  individual  is 
least  conscious  of  humidity.  Moist  air  at  a  comparatively  low  tem- 
perature, and  dry  air  at  a  higher  temperature  may  each  feel  as  warm  as 
air  of  an  intermediate  temperature  and  humidity,  but  the  comfort  ex- 
perienced in  the  three  air  conditions  would  be  different,  although  the 
effective  temperature  is  the  same. 

Air  of  proper  warmth  may,  for  instance,  contain  excessive  water  vapor, 
and  in  this  way  interfere  with  the  normal  physiologic  loss  of  moisture 
from  the  skin,  leading  to  damp  skin  and  clothing  and  producing  more  or 
less  discomfort;  or  the  air  may  be  excessively  dry,  producing  appreciable 
discomfort  to  the  mucous  membrane  of  the  nose  and  to  the  skin  which 
dries  up  and  becomes  chapped  from  too  rapid  loss  of  moisture. 

The  numerical  value  of  the  effective  temperature  index  for  any  given 
air  condition  is  fixed  by  the  temperature  of  calm  (15  to  25  fpm  air  move- 
ment) and  saturated  air  which  induces  a  sensation  of  warmth  or  cold  like 
that  of  the  given  condition.  Thus,  any  air  condition  has  an  effective 
temperature  of  60  deg,  for  instance,  when  it  induces  a  sensation  of  warmth 
like  that  experienced  in  calm  air  at  60  deg  saturated  with  moisture.  The 
effective  temperature  index  cannot  be  measured  directly  but  it  is  com- 
puted from  the  dry-  and  wet-bulb  temperature  and  the  velocity  of  air 
using-  charts  (see  Figs.  1  or  2,  3  and  4)  or  tables.  The  accuracy  in  esti- 
mating effective  temperature  is  ±0.5  F,  because  the  human  organism 
cannot  perceive  smaller  temperature  differences.  Therefore,  there  is  no 
justification  in  trying  to  read  chart  values  closer  than  0,5  F,  as  this 
implies  fictitious  accuracy. 

The  charts  shown  in  Figs.  1,  2,  3  and  4  apply  to  average  normal^and 
healthy  persons  adapted  to  American  living  and  working  conditions. 
Application  is  limited  to  sedentary  or  light  muscular  activity,  and  to 
rooms  heated  by  the  usual  American  convection  methods  (warm  air, 
central  fan  and  direct  hot  water  and  steam  heating  systems)  in  which  the 
difference  between  the  air  and  wall  surface  temperatures  may  not  be  too 


"Determining  Lines  of  Equal  Comfort,  by  F.  C.  Houghten  and  C.  P.  Yaglou  (A.S.H.V.E.  TRANS- 
ACTIONS, Vol.  29,  1923,  p.  361). 

'"Cooling  Effect  on  Human  Beings  by  Various  Air  Velocities,  by  F.  C.  Houghten  and  C.  P.  Yaglou 
(A.S.H.V.E.  TRANSACTIONS,  Vol.  30,  1924,  p.  193). 

^Effective  Temperature  with  Clothing,  by  C.  P.  Yaglou  and  W.  E.  Miller  (A.S.H.V.E.  TRANS- 
ACTIONS, Vol.  31,  1925,  p.  89). 

^Effective  Temperature  for  Persons  Lightly  Clothed  and  Working  in  Still  Air,  by  F.  C.  Houghten,  W.  W. 
Teague  and  W.  E.  Miller  (A.S.H.V.E.  TRANSACTIONS,  Vol.  32, 1926,  p.  315). 

59 


HEATING   VENTILATING  AIR  CONDITIONING  GUIDE  1938 


great.  The  charts  do  not  apply  to  rooms  heated  by  radiant  method  such 
as  British  panel  system,  open  coal  fires  and  similar  usages.  They  will 
probably  not  apply  to  races  other  than  the  white  or  perhaps  to  inhabitants 
of  other  countries  where  the  living  conditions,  climate,  heating  methods, 
and  clothing  are  materially  different  than  those  of  the  subjects  employed 
in  experiments  at  the  Research  Laboratory. 


jo  SNIIVMO 


In  rooms  in  which  the  average  wall  surface  temperature  is  considerably 
below  or  above  air  temperature,  a  correction  must  be  applied  to  the 
readings  of  the  dry-bulb  thermometer  to  allow  for  such  negative  or 
positive  radiation.  In  Fig.  5  is  given  the  cooling  effect  of  cold  walls  as 
determined  at  the  A.S.H.V.E.  Research  Laboratory"  by  trained  subjects 


l  McDennott 


60 


CHAPTER  3.   PHYSICAL  &  PHYSIOLOGICAL  PRINCIPLES  or  AIR  CONDITIONING 

passing  back  and  forth  from  a  small  experimental  room  having  three  cold 
walls,  to  a  control  room  with  walls  and  air  at  the  same  temperature. 

It  can  be  seen  in  Fig.  5  that  with  air  and  walls  at  70  F  in  the  control 
(warm  wall  room),  the  cooling  effect  of  three  cold  walls  at  55  F  of  the 
experimental  room  was  4  F.  Therefore,  for  the  same  feeling  of  warmth, 


3  S  * 

aiv  AHQ  jo  amod  *ad  3arusiow  jo  SNivyo 


the  temperature  in  the  experimental  room  should  be  increased  to  74  F. 
The  reverse  would  hold  in  rooms  with  high-wall  surface  temperature;  a 
lower  air  temperature  would  be  required  to  compensate  for  positive 
radiations  to  the  occupants. 


61 


HEATING  VENTIULTING   AIR  CONDITIONING   GUIDE  1938 


OPTIMUM  Affi  CONDITIONS 

No  single  comfort  standard  can  be  laid  down  which  would  meet^  every 
need.  There  is  an  inherent  individual  variation  in  the  sensation  of 
warmth  or  comfort  felt  by  persons  when  exposed  to  an  identical  atmos- 
pheric condition.  The  state  of  health,  age,  sex,  clothing,  activity,  and 


AHQ  JO  QNnOd    H3d   3Ur>JLSIOfl   JO  SNIVdO 


the  degree  of  acquired  adaptation  seem  to  be  the  important  factors 
affecting  the  comfort  standards, 

Since  the  prolonged  effects  of  temperature,  humidity  and  air  move- 
ment on  health  are  not  known  to  the  same  extent  as  their  effects  on  com- 
fort, the  optimum  conditions  for  health  may  not  be  identical  with  those 
for  comfort.  On  general  physiologic  grounds,  however,  the  two  do  not 
differ  greatly  since  this  is  in  accordance  with  the  efficient  operation  of  the 

62 


CHAPTER  3.   PHYSICAL  &  PHYSIOLOGICAL  PRINCIPLES  OF  AIR  CONDITIONING 

heat  regulating  mechanism  of  the  body.  This  belief  is  strengthened  by 
results  of  studies  on  premature  infants  over  a  four-year  period24.  By 
adjusting  the  temperature  and  humidity  so  as  to  stabilize  the  body  tem- 
perature of  these  infants,  the  incidence  of  diarrhoea  and  mortality  was 
decreased,  gains  in  body  weight  increased  and  infections  were  reduced 
to  a  minimum. 

Winter  Comfort  Zone  and  Comfort  Line 

In  Fig.  6  is  shown  the  A.S.H.V.E.  winter  comfort  zone  which  was 
determined  experimentally  with  large  groups  of  men  and  women  subjects 
wearing  customary  indoor  winter  clothing.  The  extreme  comfort  zone 
includes  conditions  between  60  and  74  deg  ET  in  which  one  or  more  of  the 
experimental  subjects  were  comfortable.  The  average  comfort  zone 


WALL  TEMPERATURE,  DEG  FAHR 


FIG.  5.    COOLING  EFFECT  OF  THREE  COLD  WALLS  IN  A  SMALL  EXPERIMENTAL  ROOM, 

AS  DETERMINED  BY  COMPARISON  WITH  SENSATIONS  IN  A  ROOM  OF  UNIFORM 

WALL  AND  AIR  TEMPERATURE 

includes  conditions  between  63  and  71  deg  ET  conducive  to  comfort  in 
50  per  cent  or  more  of  the  experimental  subjects.  The  most  popular 
effective  temperature  was  found  to  be  66  deg,  and  was  adopted  by  the 
Society25  as  the  winter  comfort  line  for  individuals  at  rest  wearing  custom- 
ary winter  clothing. 

The  comfort  line  separates  the  cool  air  conditions  to  its  left  from  the 
warm  air  conditions  to  its  right.  Under  the  air  conditions  existing  along 
or  defined  by  the  comfort  line,  the  body  is  able  to  maintain  thermal 


"Application  of  Air  Conditioning  to  Premature  Nurseries  in  Hospitals,  by  C.  P.  Yaglou,  Philip  Drinker 
and  K.  D.  Blackfan  (A.S.H.V.E.  TRANSACTIONS,  Vol.  36,  1930,  p.  383). 

»How  to  Use  the  Effective  Temperature  Index  and  Comfort  Charts  (A.S.H.V.E.  TRANSACTIONS, 
Vol.  38,  1932,  p.  410). 

63 


HEATING  VENTILATING  AIR  CONDITIONING   GUIDE  1938 


90 


,  STILL  AIR 

'      Air  Mcveirent  or  Turbulence  15  to  25  ft.  per  min. 
I  ;    A.S  H.V.E.  COMFORT  CHART 

(Cot>\ri£ht  1934} 


Average  Winter  Comfort  Zone  — 
'-— -  Average  Winter  Comfort  Line 
K//V///I      Average  Summer  Comfort  Zone 
— — —  Average  Summer  Comfort  Line 


70  80  90  TOO 

Pry  Bulb  Temperature  F 

FIG.  6.   A.S.H.V.E.  COMFORT  CHART  FOR  AIR  VELOCITIES  OF  15  TO  25  FPM 
(STILL  AIR)*>,  » 

gfn^o^ 

8hSS.  aPP  y  t0  "'  department  stores«  ^d  Belike  whe?e  the  expo^elrie^^ 

equilibrium  with  its  environment  with  the  least  conscious  sensation  to  the 
mdmdual,  or  with  the  minimum  phsyiologic  demand  on  the  heat  regulat- 
ing mechanism.  This  environment  involves  not  only  the  condition  of  the 
air  with  respect  to  temperature  and  humidity,  but  also  the  condition  of 
the  surrounding  objects  and  wall  surfaces.  The  comfort  zone  tests  were 

Zon^r^^^^^ 

CA.S.H.V.E. 


64 


CHAPTER  3.   PHYSICAL  &  PHYSIOLOGICAL  PRINCIPLES  OF  AIR  CONDITIONING 

made  in  rooms  with  wall  surface  temperatures  approximately  the  same  as 
the  room  dry-bulb  temperature.  For  walls  of  large  area  having  unusually 
high  or  low  surface  temperatures,  however,  a  somewhat  lower  or  higher 
range  of  effective  temperature  is  required  to  compensate  for  the  increased 
gain  or  loss  of  heat  to  or  from  the  body  by  radiation  as  shown  in  Fig.  5 
(See  also  Chapter  41). 

The  average  winter  comfort  line  (66  deg  ET)  applies  to  average 
American  men  and  women  living  inside  the  broad  geographic  belt  across 
the  United  States  in  which  central  heating  of  the  convection  type  is 
generally  used  during  four  to  eight  months  of  the  year.  It  does  not  apply 
to  rooms  heated  by  radiant  energy,  rooms  with  excessive  glass  area  or 
rooms  with  poorly  insulated  or  cold  walls.  Even  in  the  warm  south  and 
southwestern  climates,  and  in  the  very  cold  north-central  climate  of  the 
United  States,  ^the  comfort  chart  would  probably  have  to  be  modified 
according  to  climate,  living  and  working  conditions,  and  the  degree  of 
acquired  adaptation. 

In  densely  occupied  spaces,  such  as  classrooms,  theaters  and  audi- 
toriums, somewhat  lower  temperatures  may  be  necessary  than  those 
indicated  by  the  comfort  line  on  account  of  counter-radiation  between  the 
bodies  of  occupants  in  close  proximity28. 

The  sensation  of  comfort,  insofar  as  the  physical  environment  is  con- 
cerned, is  not  absolute  but  varies  considerably  among  certain  individuals. 
Therefore,  in  applying  the  air  conditions  indicated  by  the  comfort  line, 
it  should  not  be  expected  that  all  the  occupants  of  a  room  will  feel  per- 
fectly comfortable.  When  the  winter  comfort  line  is  applied  in  accordance 
with  the  foregoing  recommendations,  the  majority  of  the  occupants  will 
be  perfectly  comfortable,  but  there  will  always  be  a  few  who  would  feel 
a  bit  too  cool  and  a  few  a  bit  too  warm.  These  individual  differences  among 
the  minority  should  be  counteracted  by  suitable  clothing. 

Air  conditions  lying  outside  the  average  comfort  zone  but  within  the 
extreme  comfort  zone  may  be  comfortable  to  certain  persons.  In  other 
words,  it  is  possible  for  half  of  the  occupants  of  a  room  to  be  comfortable 
in  air  conditions  outside  the  average  comfort  zone,  but  in  the  majority  of 
cases,  if  not  in  all,  these  conditions  will  be  well  within  the  extreme  comfort 
zone  as  determined  experimentally. 

The  comfort  chart  (Fig.  6)  applies  to  adults  between  20  and  70  years 
of  age  living  in  the  northeastern  parts  of  the  United  States.  For  pre- 
maturely born  infants,  the  optimum  temperature  varies  from  100  F  to 
75  F,  depending  upon  the  stage  of  development.  The  optimum  relative 
humidity  for  these  infants  is  placed  at  65  per  cent29.  No  data  are  yet 
available  on  the  optimum  air  conditions  for  full  term  infants  and  young 
children  up  to  school  age.  Satisfactory  air  conditions  for  these  age 
groups  are  assumed  to  vary  from  75  F  to  68  F  with  natural  indoor  humidi- 
ties. For  school  children,  the  studies  of  the  New  York  State  Commission 
on  Ventilation  place  the  optimum  air  conditions  at  66  F  to  68  F  tempera- 
ture with  a  moderate  humidity  (not  specified)  and  a  moderate  but  not 
excessive  amount  of  air  movement  (not  specified)30. 


»Loc.  Cit.  Note  27. 
a»Loc.  at.  Note  24. 
"Ventilation  (Report  N.  Y.  State  Commission  on  Ventilation.  E.  P.  Button  and  Co.,  N.  Y.,  1923). 

65 


HEATING   VENTIIIATINO   AIR  CONDITIONING   GUIDE  1938 

Satisfactory  comfort  conditions  for  men  at  work  are  found  to  vary  from 
40  deg  to  70  deg  ET,  depending  upon  the  rate  of  work  and  amount  of 
clothing  worn31.  In  hot  industries,  80  deg  ET  is  considered  the  upper 
limit  compatible  with  efficiency,  and,  whenever  possible,  this  should  be 
reduced  to  70  deg  ET  or  less. 

Summer  Comfort  Zones 

The  summer  comfort  zone  is  much  more  difficult  to  fix  than  the  winter 
zone  owing  to  the  complicating  factor  of  sweating  in  warm  weather.  A 
given  air  condition  which  is  comfortable  for  persons  with  dry  skin  and 
clothing  may  prove  too  cold  for  those  perspiring,  as  is  the  case,  for 
instance,  with  employees  and  customers  in  a  cooled  store,  restaurant,  or 
theater,  on  a  warm  summer  day.  The  conditions  to  be  maintained  in 
different  types  of  public  buildings  depend  to  a  large  extent  upon_  the  oc- 
cupants' length  of  stay  and  upon  the  prevailing  outdoor  condition. 

In  Fig.  6  is  shown  the  summer  comfort  zone  for  exposures  of  3  hours  or 
more,  after  adaptation  has  taken  place.  The  average  zone  extends  from 
66  to  75  deg  ET,  with  a  comfort  line  at  71  deg  ET,  as  determined  at  the 
Harvard  School  of  Public  Health32.  These  effective  temperatures  average 
about  4  deg  higher  than  those  found  in  winter  when  customary  winter 
clothing  was  worn.  The  variation  from  winter  to  summer  is  probably  due 
partly  to  adaptation  to  seasonal  weather  and  partly  to  differences  in  the 
clothing  worn  in  the  two  seasons. 

The  best  effective  temperature  (for  exposures  lasting  3  hours  or  more) 
was  found  to  follow  the  average  monthly  outdoor  temperature  more 
closely  than  the  prevailing  outdoor  temperature.  It  remained  at  approxi- 
mately the  same  value  in  July,  August  and  September,  and  although  the 
average  monthly  temperature  did  not  vary  much,  the  prevailing  outdoor 
temperature  ranged  from  70  F  to  99.5  F.  A  decrease  in  the  optimum 
temperature  became  apparent  only  when  the  prevailing  outdoor  tempera- 
ture fell  to  66  F,  which  is  below  the  customary  room  temperature  in  the 
United  States  for  summer  and  winter. 

Crowding  the  experimental  chamber  lowered  the  comfortable  effective 
temperature  from  70.8  deg  when  the  gross  floor  area  per  occupant  was 
44  sq  ft  and  the  air  space  380  cu  ft,  to  69.4  deg  when  the  floor  area  was 
reduced  to  14  sq  ft  and  the  air  space  to  120  cu  ft  per  occupant. 

The  basic  summer  comfort  zone,  shown  in  Fig.  6  has  more  academic 
than  practical  significance.  It  prescribes  conditions  of  choice  for  con- 
tinuous exposures,  as  in  homes,  offices,  etc.,  without  regard  to  costs, 
prevailing  outdoor  air  conditions,  and  temperature  contrasts  upon 
entering  or  leaving  the  cooled  space.  A  great  number  of  persons  seem  to 
be  content  with  a  higher  plane  of  indoor  temperature,  particularly  when 
the  matter  of  first  cost  and  cost  of  operation  of  the  cooling  plant  is  given 
due  consideration. 

According  to  previous  investigations33,  an  indoor  temperature  of  about 
80  F  with  relative  humidities  below  55  per  cent,  or  74.5  deg  ET  and  lower, 
result  in  satisfactory  comfort  conditions  in  the  living  quarters  of  a  residence, 

«Loc.  Cit.  Note  22. 
»Loc.  Cit.  Note  27. 


.       .  . 

vf  ^i?1?  of  Summer  (Doling  in  the  Research  Residence  for  the  Summer  of  1934,  by  A.  P.  Kratz,  S.  Konzo, 
M.  K.  Fahnestock  and  E.  L.  Broderick  (A.S.H.V.E.  TRANSACTIONS,  Vol.  41,  1935,  p.  207). 

66 


CHAPTER  3.   PHYSICAL  &  PHYSIOLOGICAL  PRINCIPLES  or  AIR  CONDITIONING 

and  while  this  condition  is  not  representative  of  optimum  comfort  it 
provides  for  sufficient  relief  in  hot  weather  to  be  acceptable  to  the  majority 
of  users.  Experience  in  a  number  of  air  conditioned  office  buildings, 
including  the  New  Metropolitan  Life  Building  in  New  York34,  indicates 
that  a  temperature  of  about  80  F  with  a  relative  humidity  between  45  and 
55  per  cent  (73  to  74.5  deg  ET)  is  generally  satisfactory  in  meeting  the 
requirements  of  the  employees. 

In  artificially  cooled  theaters,  restaurants,  and  other  public  buildings 
where  the  period  of  occupancy  is  short,  the  contrast  between  outdoor  and 
indoor  air  conditions  becomes  the  deciding  factor  in  regard  to  the  tem- 
perature and  humidity  to  be  maintained.  The  object  of  cooling  such 
places  in  the  summer  is  to  provide  sufficient  relief  from  the  heat  without 
causing  sensations  of  chill  or  intense  heat  on  entering  and  leaving  the 
building. 

Effective  temperatures  as  high  as  75  F  at  times  have  been  found  satis- 
factory in  very  warm  weather.  There  are  two  schools  of  thought  con- 
cerning the  relation  between  temperature  and  humidity  to  be  maintained. 
For  a  given  effective  temperature  some  engineers  including  the  operators 
of  cooling  plants  favor  a  comparatively  low  temperature  with  a  high 
humidity  as  this  results  in  a  reduction  of  refrigeration  requirements. 
Preliminary  experiments  at  the  A.S.H.V.E.  Laboratories35  would  seem  to 
indicate  no  appreciable  impairment  of  comfort  with  relative  humidities 
as  high  as  80  per  cent,  provided  the  effective  temperature  is  between 
70  and  75  deg, 

The  second  school  favors  a  higher  dry-bulb  temperature,  according^  to 
the  prevailing  outdoor  dry-bulb,  with  a  comparatively  low  humidity 
(well  below  50  per  cent) ;  the  main  purpose  being  to  reduce  temperature 
contrasts  upon  entering  and  leaving  the  cooled,  space  and  to  keep  the 
clothing  and  skin  dry.  This  second  scheme  requires  more  refrigeration 
with  the  present  conventional  type  of  apparatus. 

Current  practice  in  theatres,  restaurants,  etc.,  follows  a  schedule 
similar  to  that  shown  in  Table  2,  This  schedule  should  be  used^with  con- 
siderable judgment  depending  on  the  occupancy  and  local  climatic 
conditions.  There  are  some  indications  that  a  definite  indoor  effective 
temperature  may  be  applicable  throughout  the  cooling  season,  but 
other  observations  seem  to  show  that  changing  indoor  conditions  are 
desirable  with  violently  changing  outdoor  weather  conditions.  It  is,  in 
fact,  questionable  whether  entirely  satisfactory  air  conditions  could  be 
adduced  for  practical  use  to  meet  the  changing  requirements  of  patrons 
from  the  time  they  enter  to  the  time  they  leave  a  cooled  space.  Too 
many  uncontrollable  variables  enter  into  the  problem.  Work  now  going 
on  at  the  A.S.H.V.E.  Laboratories  and  other  interested  institutions  may 
throw  considerable  light  on  this  complex  problem.  _^ 

For  cooled  banks  and  stores  where  the  customers  come  and  go  spending 


»*The  Air  Conditioned  System  of  the  New  Metropolitan  Building— First  Summer's  Experience,  by  W.  J. 
McConnell  and  I.  B.  Kagey  (A.S.H.V.E.  TRANSACTIONS,  Vol.  40,  1934,  p.  217). 

^Comfort  Standards  for  Summer  Air  Conditioning,  by  F.  C.  Houghten  and  Carl  Gutberlet  (A.S.H.V.E. 
TRANSACTIONS,  Vol.  42,  1936,  p.  215).  Cooling  Requirements  for  Summer  Air  Conditioning,  by  F.  C. 
Houghten,  F.  E.  Giesecke,  Cyril  Tasker  and  Carl  Gutberlet  (A.S.H.V.E.  JOURNAL  SECTION,  Heating, 
Piping  and  Air  Conditioning,  December,  1936,  p.  681). 

67 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 


TABLE  2.    DESIRABLE  INSIDE  CONDITIONS  ix  SUMMER  CORRESPONDING 
TO  OUTSIDE  TEMPERATURES** 

Occupancy  Over  40  Min 

INSIDE  AIR  CONDITIONS 


DEC  F 

Effective              Dry-Bulb              Wet-Bulb 
Temperature              Deg  F         ,         Deg  F 

Dew-Point 
DegF 

Relative  Humid- 
ity Per  Cent 

100 

75                  83 
75                  82 
75                   81 
75         i         80 

66 

i      67 

68 
70 

56 
59 
61 
65 

40 
45 
51 
60 

95 

74 
74 
74 
74 
74 

82 
81 
80 
79 
78 

64 
66 
67 
68 
70 

53 
57 
60 
62 
66 

36 

44 
51 
57 
68 

90 

i 

i 

73 
73 
73 
73 

81 
80 
79 
78 

63 
64 
66 
67 

52 

54 
59 
61 

36 
41 
50 
56 

85           : 

1 

1 

72 
72 
72 
72 

80 
79 

78 
77 

61 
63 
64 
66 

48 
53 
56 
60 

32 
41 
46 
56 

80 

71 
71 
71 
71 

78 
77 
76 
75 

61 
63 
64 
66 

49 
54 
57 
61 

36 
45 
52 
61 

^Applicable  to  individuals  engaged  in  sedentary  or  light  muscular  activity. 

but  a  few  minutes  in  the  cooled  space,  observations36  indicate  a  schedule 
about  1  deg  dry-bulb  or  effective  temperature  higher  than  that  shown  in 
Table  2.  Laboratory  experiments  with  exposures  of  2  to  10  min  indicate 
temperatures  2  to  10  F  higher  than  those  in  Table  2  but  with  much  lower 
relative  humidities. 

It  should  be  kept  in  mind  that  southern  people,  with  their  more  sluggish 
heat  production  and  lack  of  adaptability,  will  demand  a  comfort  zone 
several  degrees  higher  than  that  for  the  more  active  people  of  northern 
climates.  Instead  of  the  summer  comfort  line  standing  at  71  deg  as  here 
given,  it  was  found  to  be  much  higher  for  foreigners  in  Shanghai  where 
climatic  conditions  are  similar  to  those  of  our  gulf  states.  This  difference 
in  adaptability  of  people  forms  a  very  real  problem  for  air  conditioning 
engineers.  Cooling  of  theaters,  restaurants,  and  other  public  buildings  in 
southern  climates  cannot  be  based  on  northern  standards  without  con- 
siderable modification. 

Optimum  Humidity 

Just  what  the  optimum  range  of  humidity  is,  is  a  matter  of  conjecture. 
1  here  seems  to  exist  a  general  opinion,  supported  by  some  experimental 
and  statistical  data,  that  warm,  dry  air  is  less  pleasant  than  air  of  a 


-  bv  J-  H-  Walker  (Heating 


68 


CHAPTER  3.   PHYSICAL  &  PHYSIOLOGICAL  PRINCIPLES  OF  AIR  CONDITIONING 

moderate  humidity,  and  that  it  dries  up  the  mucous  membranes  in  such 
a  way  as  to  increase  susceptibility  to  colds  and  other  respiratory  dis- 
orders 37f  38>  39t  Owing  to  the  cooling  effect  of  evaporation,  higher  tem- 
peratures are  necessary,  and  this  condition  may  lead  to  discomfort  and 
lassitude.  Moist  air,  on  the  other  hand,  interferes  with  the  normal 
evaporation  of  moisture  from  the  skin,  and  again  may  cause  a  feeling  of 
oppression  and  lassitude,  especially  when  the  temperature  is  also  high. 
For  the  premature  infant,  a  high  relative  humidity  of  about  65  per  cent  is 
demonstrably  beneficial  to  health  and  growth40  until  the  infants  reach  a 
weight  of  about  5  Ib.  No  such  clear-cut  evidence  exists  in  the  case  of 
adult  persons.  In  the  comfort  zone  experiments  of  the  A.S.H.V.E. 
Research  Laboratory,  the  relative  humidity  was  varied  between  the 
limits  of  30  and  70  per  cent  approximately,  but  the  most  comfortable 
range  has  not  been  determined.  In  similar  experiments  at  the  Harvard 
School  of  Public  Health,  the  majority  of  the  subjects  were  unable  to 
detect  sensations  of  humidity  (i.e.,  too  high,  too  low,  or  medium)  when 
the  relative  humidity  was  between  30  per  cent  and  60  per  cent  with 
ordinary  room  temperatures.  This  is  in  accord  with  studies  by  Howell41, 
Miura42  and  others. 

The  limitation  of  the  comfort  zones  in  Fig.  6  with  respect  to  humidity 
must  not  be  taken  too  seriously.  Relative  humidities  below  30  per  cent 
may  prove  satisfactory  from  the  standpoint  of  comfort,  so  long  as  ex- 
tremely low  humidities  are  avoided.  From  the  standpoint  of  health, 
however,  the  consensus  seems  to  favor  a  relative  humidity  between  40  and 
60  per  cent.  In  mild  weather  such  comparatively  high  relative  humidi- 
ties are  entirely  feasible,  but  in  cold  or  sub-freezing  weather  they  are 
objectionable  on  account  of  condensation  and  frosting  on  the  windows. 
They  may  even  cause  serious  damage  to  certain  building  materials  of  the 
exposed  walls  by  condensation  and  freezing  of  the  moisture  accumulating 
inside  these  materials.  Unless  special  precautions  are  taken  to  properly 
insulate  the  affected  surfaces,  it  will  be  necessary  to  reduce  the  degree  of 
artificial  humidification  in  sub-freezing  weather  to  less  than  40  per  cent, 
according  to  the  outdoor  temperature.  Information  on  the  prevention  of 
condensation  on  building  surfaces  is  given  in  Chapter  7.  The  principles 
underlying  humidity  requirements  and  limitations  are  discussed  more 
fully  elsewhere43. 

The  purpose  of  artificial  humidification  may  be  easily  defeated  by 
failure  to  change  the  spray  water  of  the  humidifier  at  least  daily.  Where 
this  condition  occurs,  the  air  is  characterized  by  a  lack  of  freshness,  and 
under  extreme  conditions  by  a  musty,  sour  odor  in  the  conditioned  space. 


"Reactions  of  the  Nasal  Cavity  and  Post-Nasal  Space  to  Chilling  of  the  Body  Surface,  by  Mudd,  Stuart, 
et  al  (Journal  Experimental  Medicine,  1921,  Vol.  34,  p.  11). 

^Reactions  of  the  Nasal  Cavity  and  Post-Nasal  Space  to  Chilling  of  the  Body  Surfaces,  by  A.  Goldman, 
et  al  and  Concurrent  Study  of  Bacteriology  of  Nose  and  Throat  (Journal  Infectious  Diseases,  1921,  Vol.  29, 
p.  151). 

S9The  Etiology  of  Acute  Inflammations  of  the  Nose,  Pharynx  and  Tonsils,  by  Mudd,  Stuart,  et  al  (Am. 
Otol.,  Rhinol.,  and  Laryngol.,  1921). 

«Loc.  Cit.  Note  24. 

^Humidity  and  Comfort,  by  W.  H.  Howell  (The  Science  Press,  April,  1931). 

^Effect  of  Variation  in  Relative  Humidity  upon  Skin  Temperature  and  Sense  of  Comfort,  by  U.  Miura 
(American  Journal  of  Hygiene,  Vol.  13,  1931,  p.  432). 

^Humidification  for  Residences,  by  A.  P.  Kratz,  University  of  Illinois  (Engineering  Experiment  Station 
Bulletin  No.  230,  July  28,  1931). 

69 


HEATING   VENTIIATING  AIR  CONDITIONING   GUIDE  1938 

Affi  QUALITY  AND  QUANTITY 
Air  Quality 

In  occupied  spaces  in  which  the  vitiation  is  entirely  of  human  origin, 
the  chemical  composition  of  the  air,  the  dust,  and  often  the  bacteria  con- 
tent may  be  dismissed  from  consideration  so  that  the  problem  consists  in 
maintaining  a  suitable  temperature  with  a  moderate  humidity,  and  in 
keeping  the  atmosphere  free  from  objectionable  odors.  Such  unpleasant 
odors,  human  or  otherwise,  can  be  easily  detected  by  persons  entering  the 
room  from  clean,  odorless  air. 

In  industrial  rooms  where  the  primary  consideration  is  the  control  of 
air  pollution  (dusts,  fumes,  gases,  etc.),  or  contamination  not  removable 
at  the  source  of  production,  the  clean  air  supply  must  be  sufficient  to 
dilute  the  polluting  elements  to  a  concentration  below  the  physiological 
threshold  (see  Chapters  4  and  26). 

Air  Quantity 

The  air  supply  to  occupied  spaces  must  always  be  adequate  to  satisfy 
the  physiological  requirements  of  the  occupants.  It  must  be  sufficient  to 
maintain  the  desired  temperature,  humidity,  and  purity  with  reasonable 
uniformity  and  without  drafts.  In  many  practical  instances  there  are 
two  air  quantities  to  be  considered,  (a)  outdoor  air  supply,  and  (b)  total 
air  supply.  The  difference  between  the  two  gives  the  amount  of  air  to  be 
recirculated. 

When  the  only  source  of  contamination  is  the  occupant,  the  minimum 
quantity  of  outdoor  air  needed  appears  to  be  that  necessary  to  remove 
objectionable  body  odors,  or  tobacco  smoke.  The  concentration  of  body 
odor  in  a  room,  in  turn,  depends  upon  a  number  of  factors,  including 
socio-economic  status  of  occupants,  outdoor  air  supply,  air  space  allowed 
per  person,  odor  adsorbing  capacity  of  air  conditioning  processes,  tem- 
perature, and  other  factors  of  secondary  importance.  With  any  given 
group  of  occupants  and  type  of  air  conditioner  the  intensity  of  body  odor 
perceived  upon  entering  a  room  from  relatively  clean  air  was  found  to 
vary  inversely  with  the  logarithm  of  outdoor  air  supply  and  the  logarithm 
of  the  air  space  allowed  per  person* 

The  minimum  outdoor  air  supply  necessary  to  remove  objectionable 
body  odors  under  various  conditions,  as  determined  experimentally  at  the 
Harvard  School  of  Public  Health44,  is  given  in  Table  3. 

Outdoor  air  requirements  for  the  removal  of  objectionable  tobacco 
smoke  odors  have  yet  to  be  determined.  Practical  values  in  the  field  vary 
from  5  to  15  cfm  per  person;  this  air  quantity  may  and  should  be  a  part 
of  that  necessary  for  other  requirements,  i.e.,  removal  of  body  odors,  heat, 
moisture,  etc. 

The  total  quantity  of  air  to  be  circulated  through  an  enclosure  is 
governed  largely^  by  the  needs  for  controlling  temperature  and  air  dis- 
tribution when  either  heating  or  cooling  is  required.  The  factors  which 
determine  total  air  quantity  include  the  type  and  nature  of  the  building, 
locality,  climate,  height  of  rooms,  floor  area,  window  area,  extent  of 
occupancy,  and  last  but  not  least,  the  method  of  distribution. 

Serious  difficulties  are  often  encountered  in  attempting  to  cool  a  room 

**Loc.  Cit  Note  3. 

70 


CHAPTER  3.  PHYSICAL  &  PHYSIOLOGICAL  PRINCIPLES  OF  AIR  CONDITIONING 


with  a  poor  distribution  system  or  with  an  air  supply  which  is  too  small  to 
result  in  uniform  distribution  without  drafts.  Some  systems  of  distribu- 
tion produce  drafts  with  but  a  few  degrees  temperature  rise,  while  other 
systems  operate  successfully  with  a  temperature  rise  as  high  as  35  F. 
The  total  air  quantity  introduced  in  any  particular  case  is  inversely  pro- 
portional to  the  temperature  rise,  and  depends  largely  upon  the  judgment 
and  ingenuity  of  the  engineer  in  designing  the  most  suitable  system  for  the 
particular  conditions. 

TABLE  3.    MINIMUM  OUTDOOR  AIR  REQUIREMENTS  TO  REMOVE  OBJECTIONABLE 

BODY  ODORS 

(Provisional  values  subject  to  revision  upon  completion  of  work) 


TYPE  OP  OCCUPANTS 


AIR  SPACE  PER 
PEBSON  Cu  FT 


OUTDOOR*  AIR  SUPPLY 
CFM  ?BR  PERSON 


Heating  season  with  or  without  recirculation.   Air  not  conditioned. 


Sedentary  adults  of  average  socio-economic  status  
Sedentary  adults  of  average  socio-economic  status  

100 
200 

25 
16 

Sedentary  adults  of  average  socio-economic  status  — 
Sedentary  adults  of  average  socio-economic  status.  

300 
500 

12 
7 

Laborers 

200 

23 

Grade  school  children  of  average  class  

100 

29 

Grade  school  children  of  average  class  
Grade  school  children  of  average  class  

200 
300 

21 
17 

Grade  school  children  of  average  class  

500 

11 

Grade  school  children  of  poor  class  

200 

38 

Grade  school  children  of  better  class  

200 

18 

Grade  school  children  of  best  class  

100 

22 

Heating  season.  Air  humidified  by  means  of  centrifugal  humidifier.  Water 
atomization  rate  8  to  10  gph.    Total  air  circulation  SO  cfm  per  person. 


Sedentary  Adults  

200 

12 

Summer  season.  Air  cooled  and  dehumidified  by  means  of  a  spray  dehumidifier. 
Spray  water  changed  daily.    Total  air  circulation  80  cfm  per  person. 


Sedentary  Adults  

200 

<4 

a  Impressions  upon  entering  room  from  relatively  clean  air  at  threshold  odor  intensity. 


The  changes  in  moisture  content  resulting  from  occupation  in  the 
atmosphere  of  a  room  supplied  with  various  volumes  of  outside  air  is 
shown  in  Fig.  7.  Data  are  given  for  an  adult,  5  ft  8  in.  in  height,  weighing 
150  Ib  and  having  a  body  surface  of  19.5  sq  ft  and  for  a  child,  12  years  of 
age,  4  ft  7  in.  in  height  weighing  76.6  Ib  and  having  a  body  surface  area 
of  12.6  sq  ft.  Also  given  in  Fig.  7  is  the  temperature  of  incoming  air 
necessary  to  maintain  a  room  temperature  of  either  70  or  80  F  as  indicated 
assuming  that  there  is  no  heat  gain  or  loss  to  the  room  by  transmission 
through  the  walls,  solar  radiation  or  other  sources. 

71 


HEATING  VENTILATING   AIR  CONDITIONING   GUIDE  1938 


AIR  MOVEMENT  AND  DISTRIBUTION 

Stagnant  warm  air,  no  matter  how  pure,  is  not  stimulating  and  it 
detracts  to  some  extent  from  the  quality  of  air.  Experience,  and  recent 
field  studies  by  the  A.S.H.V.E.  Research  Laboratory45  place  the  desirable 
air  movement  between  15  and  25  fpm  under  ordinary  room  temperatures 
during  the  heating  season.  Objectionable  drafts  are  likely  to  occur  when 
the  velocity  of  the  air  current  is  40  fpm  and  the  temperature  of  the  air 
current  2  F  or  more  below  the  customary  winter  room  temperature. 
Higher  velocities  are  not  objectionable  in  the  summer  time  when  the  air 


i — i — i 

ADULTS    IN    80 F    AIR 


!>CHILDREN     IN    80  F    AIR 


.ADULTS     IN     70  F    AIR 
(^.CHILDREN     IN     70  F    AIR 


CHILDREN     IN    80  F    AIR 


ULTS    IN    80 F    AIR 


CHILDREN     IN     70  F    AIR 


ADULTS     IN     70  F    AIR 


12  16  20  24  28- 

RATE    OF     AIR    SUPPLY 
CUBIC  FEET  PER  MINUTE  PER  OCCUPANT 

FIG.  7.    RELATION  AMONG  RATE  OF  AIR  CHANGE  PER  OCCUPANT,  MOISTURE  CONTENT 
OF  ENCLOSURE,  AND  DRY-BULB  TEMPERATURE  OF  INCOMING  AIR 

temperature  exceeds  80  F.  Variations  in  air  movement  and  temperature 
in  different  parts  of  occupied  rooms  are  often  indicative  of  relative  air 
distribution.  The  work  of  the  A.S.H.V.E.  Research  Laboratory  indicates 
that  an  air  movement  between  15  and  25  fpm  with  a  temperature  variation 
of  3  F  or  less  in  different  parts  of  a  room,  36  in.  above  floor,  insure  satis- 
factory distribution.  Considerable  evidence  was  obtained  in  these  tests 
to  show  that  measurements  of  carbon  dioxide  are  not  essential  for  the 
study  of  air  distribution,  or  for  indirect  measurements  of  outdoor  air 


^Classroom  Drafts  in  Relation  to  Entering  Air  Stream  Temperature,  by  F.  C.  Houghten, 
Cart  Gutberlet  and  M.  F.  Lichtenfels  (A.S.H.V.E.  TRANSACTIONS,  Vol.  41,  1935,  p.  268). 


,  H.  H.  Trimble, 


72 


CHAPTER  3.   PHYSICAL  &  PHYSIOLOGICAL  PRINCIPLES  or  AIR  CONDITIONING 


TABLE  4.    RELATION  BETWEEN  METABOLIC  RATE  AND  ACTIVITY* 


ACTIVITY 

HOTJRLT  META- 
BOLIC RATE  FOB 
AYG.  PERSON  OB 
TOTAL  HEAT 
DISSIPATED, 
BTU  PER  HOUR 

HOURLT 

SENSIBLE 
HEAT 
DISSIPATED, 
BTU  PER 
HOUR 

HOURLY 
LATENT 
HEAT 
DISSIPATED, 
BTU  PER 
HOUR 

MOISTURE  DISSIPATED, 
PER  HOUR 

GRAINS 

LB 

Average  Person  Seated  at  Rest1.. 
Average  Person  Standing  at  Rest1 

384 
431 

225 
225 

159 
206 

1070 
1390 

0.153 

0.199 

Tailor2           

482 

225 

257 

1740 

0.248 

Office  Worker  Moderately  Active 

490 

225 

265 

1790 

0.256 

Clerk,  Moderately  Active, 

Standing  at  Counter.—  

600 

225 

375 

2530 

0.362 

Book  Binder2.  

626 

225 

401 

2710 

0.387 

Shoe  Maker2;  Clerk,  Very  Active 

Standing  at  Counter  

661 

225 

436 

2940 

0.420 

Pool  Player  

680 

230 

450 

3040 

0.434 

Walking^  mph3.  4;  Light 

Dancing         

761 

250 

511 

3450 

0.493 

Metalworker2  

862 

277 

585 

3950 

0.564 

Painter  of  Furniture2.  

876 

280 

596 

4020 

0.575 

Restaurant  Serving,  Very  Busy.. 

1000 

325 

675 

4560 

0.651 

Walking  3  mph8  

1050 

346 

704 

4750 

0.679 

Walking  4  mph8.  *;  Active 
Dancing,  Roller  Skating.  

1390 

452 

938 

6330 

0.904 

Stone  Mason2  

1490 

490 

1000 

6750 

0.964 

Bowling  

1500 

490 

1010 

6820 

0.974 

Man  Sawing  Wood2.  

1800 

590 

1210 

8170 

1.167 

Slow  Run4  

2290 

Walking  5  mph8  

2330 

Vgry  Severe  Exercise**  

2560 

Maximum  Exertion  Different 

People4.  

3000  to  4800 

aMetabolism  rates  noted  based  on  tests  actually  determined  from  the  following  authoritative  sources: 
iA.S.H.V.E.  Research  Laboratory;  *Becker  and  Hamalainen;  'Douglas,  Haldane,  Henderson  and  Schneider; 
^Henderson  and  Haggard;  and  "^Benedict  and  Carpenter.  Metabolic  rates  for  other  activities  estimated. 
Total  heat  dissipation  integrated  into  latent  and  sensible  rates  by  actual  tests  for  metabolic  rates  up  to 
1250  Btu  per  hour,  and  extrapolated  above  this  rate.  Values  for  total  heat  dissipation  apply  for  all  atmos- 
pheric conditions  in  a  temperature  range  from  approximately  60  to  90  F  dry-bulb.  Division  of  total  heat 
dissipation  rates  into  sensible  and  latent  heat  holds  only  for  conditions  having  a  dry-bulb  temperature  of 
79  F.  For  lower  temperatures,  sensible  heat  dissipation  increases  and  latent  heat  decreases,  while  for 
higher  temperatures  the  reverse  is  true. 


TABLE  5. 


DEGREES  OF  PERSPIRATION  FOR  PERSONS  SEATED  AT  REST  UNDER 
VARIOUS  ATMOSPHERIC  CONDITIONS 


DEGREE  OF  PERSPIRATION* 

ATMOSPHERIC  CONDITION 

95  Per  Cent  Relative 
Humidity 

20  Per  Cent  Relative 
Humidity 

E.T. 

D.B. 

W.B. 

E.T. 

D.B. 

W.B. 

Forehead  clammy  ..  

73.0 
73.0 
79.0 
80.0 
84.5 
88.0 
88.5 

73.6 
73.6 
79.7 
80.8 
85.4 
89.0 
89.5 

72.4 
72.4 
78.4 
79.4 
84.0 
87.6 
88.1 

75.0 
75.0 
81.0 
87.0 
86.5 
94.0 
90.0 

87.0 
87.0 
97.5 
109.4 
108.5 
125.2 
116.0 

60.7 
60.7 
67.5 
75.2 
74.6 
85.4 
79.5 

Body  clammy..  .  .  
Body  damp                              .         .—  —  - 

Beads  on  forehead  
Body  wet.    

Perspiration  on  forehead  runs  and  drips  
Perspiration  runs  down  body-  .  

•Forty  per  cent  of  subjects  registered  degree  of  perspiration  equal  to  or  greater  than  indicated. 

73 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


!  1  '  ' 

-H~~*" 
JTU- 

*—  U 

1   !   '   |   '  M    ~ 

'  I  '  !  '  •  '  i 
,  '  '  •  '    ^ 

—^  ;•  "'-•y^i- 

p-r-  :  ,  i  i  I  n  I  ,  J  | 
.1  «;':,•';!'  —  i  i  >  L 

1  '  '  '  '  ^ 

•  :  JT  ''^ 

!  i  •  '  i  >^r  i  M$ 

'  l^^^i  : 

ni;b/ffl  li 

wm 

&L-"--- 

:^::::fe 

"Ib 

—  '  — 
,  1 
-^-H- 

—  1  '  ' 

"t~h~ 

L-in 

jf 

r4- 

T^ 

^ 

d 

^c 

-r 

4 

s 

ft 

jT 

s     f 

'  I  :   /  / 
1  'A  A 

£H4# 

!/   /  j 

/        j 

I/I  '  1  1  1 

ijr^i.y-  *  \ 

/.SiA'fo  i  -r^ 
lJTT!1f  MM 

/  '  i  /[  *  '  '  —  i  
7  —  y-  -HI  —  H-I  — 

M  j  ,  1  ,  .  |  1  

TTrmTr 

b 

-  ;^ 
::"::__  b 

44- 

1  III 

1  j  J 

i-LJL 

1 

Y 

1 

- 

^M  4- 

p> 

I  11 


. 


fefe    g««    *3sfs 
§   ^g|  3  .|I|g 

8"     w  o  d    ^sf  Sc 
?2,S    ^fel^^a 


8      8      §     8      § 

o«oio-^<ON- 
ClJt>s"S5D    NVW   39VU3AV  «0d    'BH   H3d     Til*  "VIOL 


05  B 


oooooo 
oooooo 
—  o»cor*<o 

OJT35SBD    NVW   39VH3AV  tJO 


oo 
oo 
evi  — 

U3d    TO  IB    TV1QI 


74 


CHAPTER  3.    PHYSICAL  &  PHYSIOLOGICAL  PRINCIPLES  OF  AIR  CONDITIONING 


TABLE  6.    DEGREES  OF  PERSPIRATION  FOR  PERSONS  AT  WORK  UNT»ER  VARIOUS 
ATMOSPHERIC  CONDITIONS 

Work  Rate  83,000  Ft  Lb  per  Hour 


DEGREE  OF  PERSPIRATION" 

95  Per  Cent  Relative 
Humidity 

20  Per  Cent  Relative 
Humidity 

E.  T. 

D.B. 

W.B. 

•E.  T. 

D.B. 

W.B 

Forehead  clammy  

59.0 
50.0 
60.0 
68.0 
69.0 
78.5 
79.0 

59.4 
50.2 
60.3 
68.5 
69.6 
79.3 
79.8 

58.3 
49.3 
59.3 
67.5 
68.5 
78.0 
78.5 

69.5 
57.0 
62.5 
76.0 
71.0 
82.0 
81.0 

80.5 
61.6 
69.6 
91.0 
82.8 
100.5 
99.8 

56.5 
44.2 
49.5 
63.4 
53.0 
70.2 
69.0 

Body  clammy  
Body  damp  .  .  
Beads  on  forehead.    

Body  w^t 

Perspiration  on  forehead  runs  and  drips  
Perspiration  runs  down  body  

ATMOSPHERIC  CONDITION 


aForty  per  cent  of  subjects  registered  degree  of  perspiration  equal  to  or  greater  than  indicated. 

supply,  which  can  be  obtained  more  conveniently  from  the  increase  in 
moisture  content  of  the  ventilating  current. 


HEAT  AND  MOISTURE  GIVEN  UP  BY  HUMAN  BODY 

In  conditioning  air  for  comfort  and  health  it  is  necessary  to  know  the 
rate  of  sensible  and  latent  heat  liberation,  from  the  human  body,  which  in 
conjunction  with  other  heat  loads  (see  Chapters  5  and  7)  determine  the 
capacity  of  the  conditioner.  The  data  in  common  use  are  those  of  the 
A.S.H.V.E.  Research  Laboratory46  shown  in  Figs.  8,  9,  10  and  11.  Other 
useful  data  are  given  in  Tables  4,  5  and  6,  which  are  self-explanatory. 

ULTRA-VIOLET  RADIATION  AND  IONIZATION 

In  spite  of  the  rapid  advances  in  the  field  of  air  conditioning  during  the 
past  few  years,  the  secret  of  reproducing  indoor  atmospheres  of  as 
stimulating  qualities  as  those  existing  outdoors  under  ideal  weather  con- 
ditions, has  not  as  yet  been  found.  Extensive  studies  have  failed  to 
elucidate  the  cause  of  the  stimulating  quality  of  country  air,  qualities 
which  are  lost  when  such  air  is  brought  indoors  and  particularly  when  it 
is  handled  by  mechanical  means.  Ultra-violet  light  and  ionizatlon  have 
been  suggested  but  the  evidence  so  far  is  inconclusive  or  negative47. 


*6Thermal  Exchanges  between  the  Bodies  of  Men  Working  and  the  Atmospheric  Environment,  by  F.  C. 
Houghten,  W.  W.  Teague,  W.  E.  Miller  and  W.  P.  Yant  (American  Journal  of  Hygiene,  Vol.  XIII,  No.  2. 
March,  1931,  pp.  415-431). 

47Changes  in  Ionic  Content  in  Occupied  Rooms,  Ventilated  by  Natural  and  Mechanical  Methods,  by 
C.  P.  Yaglou,  L.  C.  Benjamin  and  S.  P.  Choate  (A.S.H.V.E.  TRANSACTIONS,  Vol.  38, 1932,  p.  191).  Physio- 
logic Changes  During  Exposure  to  Ionized  Air,  by  C.  P.  Yaglou,  A.  D.  Brandt  and  L.  C.  Benjamin  (A.S. 
H.V.E.  TRANSACTIONS,  Vol.  39,  1933,  p.  357).  Diurnal  and  Seasonal  Variations  in  the  Small  Ion  Content 
of  Outdoor  and  Indoor  Air,  by  C.  P.  Yaglou  and  L.  C.  Benjamin  (A.S.H.V.E.  TRANSACTIONS,  Vol.  40, 
1934,  p.  271).  The  Nature  of  Ions  in  Air  and  Their  Possible  Physiological  Effects,  by  L/.  B.  Loeb  (A.S. 
H.V.E.  TRANSACTIONS,  Vol.  41,  1935,  p.  101).  The  Influence  of  Ionized  Air  upon  Normal  Subjects,  by 
L.  P.  Herrington  (Journal  Clinical  Investigation,  14,  January,  1935).  The  Effect  of  High  Concentrations 
of  Light  Negative  Atmospheric  Ions  on  the  Growth  and  Activity  of  the  Albino  Rat,  by  L.  P.  Herrington 
and  Karl  L.  Smith  (Journal  Ind.  Hygiene,  17,  November,  1935).  Subjective  Reactions  of  Human  Beines 
to  Certain  Outdoor  Atmospheric  Conditions,  by  C.-E.  A.  Winslow  and  L.  P.  Herrington  (A.S.H.V.E. 
TRANSACTIONS,  Vol.  42,  1936,  p.  119). 

75 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


^1000 

"-i  i"<  —  *—  t'  'jx^T  F 

H 

I        ,       !  M       ,'        " 

U. 

gonn 

,  .  y^;       -,     - 

900 

,        L.      I        ,                 I        '         ,'        |         ,        !        '                 ,         !        I 

jf    i  i       _; 

—  Ann 

,                    .     i/Lj 

1  ;  '  i     '       /  '  i 

i   .            /     ^     -5000 

S      *VA/> 

1           '        j/1  f 

/             ^  z 

i                    i  X  ' 

o 

•  •   rii   ,  |   /!     :  • 

j  ;  .  ;  j>"  _  _,  ^    - 

<  600 

1    .  'i  1  •  :  i  1  !/|  .    |  i 

/My^          ^                             - 

fj     y  i    X^^T  - 

50O 

i               '  !  J              '      '  / 

g 

2       t 

^~  yf                          _3000 

cf  40° 

-j- 

!  '      /             /  '' 

y~"  ;-" 

1      I 

--U. 

--J-H 

f~l~  .x  T  ~^~^^  ^ 

-r- 

£  300: 

x 

| 

r  r--E-2ooo 

*•       £ 

=**oo 

L 

L.-JL-L-f?-^  

-g__X  = 

at 

-h- 

4L*£'i£*-l  L.J. 

i-  E-iooo 

<!> 

DRY   BULB    TEMPELRATURE    *FAHR.  g 

FIG.  10.   LATENT  HEAT  AND  MOISTURE  Loss  FROM  THE  HUMAN  BODY  BY  EVAPORATION 
IN  RELATION  TO  DRY-BULB  TEMPERATURE  FOR  STILL  AIR  CoNDiTioNSa 


/-  -A.TMen  working  66,150  ft-Ib  per  hour.    Curve  B — Men  working  33,075  ft-lb  per  hour.    Curve 

C— Men  working  16,638  ft-lb  per  hour.  Curve  D— Men  seated  at  rest.  Curves  A  and  C  drawn  from  data 
at  a  dry-bulb  temperature  of  81.3  F  only  and  extrapolating  the  relation  between  Curves  B  and  D  which 
were  drawn  from  data  at  many  temperatures. 


45°        50°        55°        60°        65°        70°        75° 
DRY   BULB    TEMPERATURE     *FAHR. 


£OSS  *ROM  rai5  HUMAN  BODY  BY  EVAPORATION,  RADIATION  AND  CON- 
RELATION TO  DRY-BULB  TEMPERATURE  FOR  STILL  AIR  CONDITION^ 


76 


CHAPTER  3.   PHYSICAL  &  PHYSIOLOGICAL  PRINCIPLES  OF  AIR  CONDITIONING 


NATURAL  AND  MECHANICAL  VENTILATION 

Under  favorable  conditions  natural  ventilation  methods  properly  com- 
bined with  means  for  heating  may  be  sufficient  to  provide  for  the  fore- 
going objectives  in  homes,  uncrowded  offices,  small  stores,  etc. 

In  large  offices,  large  school  rooms,  and  in  public  and  industrial  build- 
ings, natural  ventilation  is  uncertain  and  makes  heating  difficult.  The 
chief  disadvantage  of  natural  methods  is  the  lack  of  control ;  they  depend 
largely  on  weather  and  upon  the  velocity  and  direction  of  the  wind. 
Rooms  on  the  windward  side  of  a  building  may  be  difficult  to  heat  and 
ventilate  on  account  of  drafts,  while  rooms  on  the  leeward  side  may  not 
receive  an  adequate  amount  of  air  from  out-of-doors.  The  partial  vacuum 
produced  on  the  leeward  side  under  the  action  of  the  wind  may  even 
reverse  the  flow  of  air  so  that  the  leeward  half  of  the  building  has  to  take 
the  drift  of  the  air  from  the  rooms  of  the  windward  half.  Under  such 
conditions  no  outdoor  air  would  enter  through  a  leeward  window  opening, 
but  room  air  would  pass  out. 

In  warm  weather  natural  methods  of  ventilation  afford  little  or  no 
control  of  indoor  temperature  and  humidity.  Outdoor  smoke,  dust  and 
noise  constitute  other  limitations  of  natural  methods. 

RECmCULATION  AND  OZONE 

The  amount  of  recirculated  air  may  be  varied  to  suit  changes  in  weather 
and  seasonal  requirements,  so  as  to  conserve  heat  in  winter  and  refrig- 
eration in  summer,  but  the  saving  in  operating  cost  should  not  be  obtained 
at  the  expense  of  air  quality. 

Ozone  has  been  used  for  deodorizing  recirculated  air  by  oxidation  or 
masking.  Under  favorable  conditions  some  success  is  possible  but  from 
the  practical  standpoint  it  is  difficult  to  regulate  the  ozone  output  so  as  to 
just  neutralize  undesirable  odors  at  all  times  during  the  occupancy  of  a 
room.  The  difficulties  appear  to  be  mainly  due  to  a  wide  variability  in 
the  rate  of  ozone  disappearance  in  different  rooms,  or  in  the  same  room  at 
different  times,  according  to  the  characteristics  of  a  room,  the  absolute 
humidity,  impurities  in  the  air,  number  and  type  of  occupants,  and 
probably  other  factors  which  require  considerable  study  before  ozone  can 
be  safely  and  economically  applied. 

The  allowable  concentrations  in  the  breathing  zone  are  very  small, 
between  0.01  to  0.05  parts  of  03  per  million  parts  of  air.  These  are  much 
too  small  to  influence  bacteria.  Higher  concentrations  are  associated 
with  a  pungent  unpleasant  odor  and  considerable  discomfort  to  the 
occupants.  One  part  per  million  causes  respiratory  discomfort  in  man, 
headaches  and  depression,  lowers  the  metabolism,  and  may  even  lead  to 
coma48. 

Toilets,  kitchens,  and  similar  rooms,  in  buildings  using  recirculation, 
should  be  ventilated  separately  by  mechanical  exhaust  in  order  to  prevent 
objectionable  odors  from  diffusing  into  other  parts  of  the  building. 


**The  British  Medical  Journal.  Editorial.  June  25,  1932,  p.  1182.    See  also  Loc.  Cit.  Note  5. 

77 


HEATING   VENTILATING  AIR  CONDITIONING  GUIDE  1938 
PROBLEMS  IN  PRACTICE 

1  •  What  are  the  most  comfortable  air  conditions? 

Comfort  standards  are  not  absolute,  but  they  are  greatly  affected  by  the  physical  con- 
dition of  the  individual,  and  the  climate,  season,  age,  sex,  clothing,  and  physical  activity. 
For  the  northeastern  climate  of  the  United  States,  the  conditions  which  meet  the  require- 
ments of  the  majority  of  people  consist  of  temperatures  between  68  and  72  F  in  winter 
and  between  70  and  85  F  in  summer,  the  latter  depending  largely  upon  the  prevailing 
outdoor  temperature.  The  most  desirable  relative  humidity  range  seems  to  be  between 
30  and  60  per  cent. 

2  •  Are  the  optimum  conditions  for  comfort  identical  with  those  for  health? 

There  are  no  absolute  criteria  of  the  prolonged  effects  of  various  air  conditions  on  health. 
For  the  present  it  can  be  only  inferred  that  bodily  discomfort  may  be  an  indication  of 
adverse  conditions  leading  to  poor  health. 

3  •  Given  dry-bulh  and  wet-bulb  temperatures  of  76  F  and  62  F,  respectively, 
and  an  air  velocity  of  100  fpm,  determine:    (l)  effective  temperature  of  the 
condition;  (2)  effective  temperature  with  calm  air;  (3)  cooling  produced  hy  the 
movement  of  the  air. 

(1)  In  Fig.  1  draw  line  AB  through  given  dry-  and  wet-bulb  temperatures.  Its  inter- 
section with  the  100  ft  velocity  curve  gives  69  deg  for  the  effective  temperature  of  the 
condition.  (2)  Follow  line  AB  to  the  right  to  its  intersection  with  the  20  fpm  velocity 
line,  and  read  70.4  deg  for  the  effective  temperature  for  this  velocity  or  so-called  still  air. 
(3)  The  cooling  produced  by  the  movement  of  the  air  is  70.4  -  69  =  1.4  deg  ET. 

4  •  Assume  that  the  design  of  an  air  conditioning  system  for  a  theater  is  to  he 
based  on  an  outdoor  dry-bulb  temperature  of  95  F  and  a  wet-bulb  temperature 
of  78  F  with  an  indoor  relative  humidity  of  50  per  cent.    According  to  Table  2, 
the  dry-bulb  temperature  in  the  auditorium  should  be  80  F.    Estimate  the 
sensible  and  latent  heat  given  up  per  person. 

The  sensible  heat  given  up  per  person  per  hour  may  be  obtained  from  Fig.  9.  With  an 
abscissa  value  of  80  F,  Curve  D  for  men  seated  at  rest  gives  a  value  (on  the  ordinate 
scale)  of  220  Btu  per  person  per  hour  as  the  sensible  heat  loss.  The  latent  heat  given  up 
by  a  person  seated  at  rest  may  be  obtained  from  Fig.  10.  With  an  abscissa  value  of  80  F,  ' 
Curve  D  indicates  a  latent  heat  loss  of  175  Btu  per  hour  (left  hand  scale)  or  a  moisture 
loss  of  1190  grains  per  hour  (right  hand  scale). 

5  •  Neglecting  the  gain  or  loss  of  heat  by  transmission  or  infiltration  through 
walls,  windows  and  doors,  how  many  cubic  feet  of  outside  air,  with  dry-  and 
wet-bulb  temperatures  of  65  F  and  59  F,  respectively,  (63.1  deg  ET)  must  be 
supplied  per  hour  to  an  auditorium  containing  1000  people  in  order  that  the 
inside  temperature  shall  not  exceed  75  F  dry-bulb  and  65  F  wet-bulb? 

Figs.  9  and  10  give  265  Btu  sensible  heat  and  905  grains  of  moisture  per  person  with  a 
dry-bulb  temperature  of  75  F  in  the  auditorium.  Therefore,  265,000  Btu  of  sensible 
heat  and  905,000  grains  of  moisture  will  be  added  to  the  air  in  the  auditorium  per  hour. 

Taking  0,24  as  the  specific  heat  of  air,  2.4  Btu  per  pound  of  air  will  be  absorbed  in 
raising  the  dry-bulb  temperature  from  65  to  75  F,  and  265,000  -4-  2.4  -  110,400  Ib  of 
air  or  110,400  X  13.4  =  1,479,000  cfh  of  air  will  be  required.  This  is  equivalent  to 
1,479,000  -5-  (1000  X  60)  =  24.7  cfm  per  person. 

The  ^moisture  content  of  the  inside  air  is  76  grains  per  pound  of  dry  air  and  that  of  the 
outside  condition  is  65  grains.  From  a  psychrometric  chart  the  increase  in  moisture 
content  will  therefore  be  11  grains  per  pound  of  dry  air.  Hence  905,000  +  11.0  =  82,300 
Ib  of  air  at  the  specified  condition  will  be  required.  This  is  equivalent  to  82,300  X  13  4 
-  1,103,000  cfh  of  air  or  1,103,000  --  (1000  X  60)  -  18.4  cfm  of  air  per  person. 

The  higher  volume  of  24.7  cfm  per  person  will  be  required  to  keep  the  dry-bulb  tem- 
perature from  rising  above  the  75  F  specified.  The  wet-bulb  temperature  will  therefore 
not  rise  to  the  maximum  of  65  F. 


78 


Chapter  4 

AIR  POLLUTION 

Classification   of  Air  Impurities,   Dust   Concentrations,   Air 

Pollution  and  Health,  Occlusion  of  Solar  Radiation,  Smoke 

and  Air  Pollution  Abatement,  Dust  and  Cinders,  Nature's 

Dust  Catcher 

THE  particulate  impurities  which  contribute  to  atmospheric  pollution 
include  carbon  from  the  combustion  of  fuels,  particles  of  earth,  sand, 
ash,  rubber  tires,  leather,  animal  excretion,  stone,  wood,  rust,  paper, 
threads  of  cotton,  wool,  and  silks,  bits  of  animal  and  vegetable  matter, 
and  pollen.  Microscopic  examination  of  the  impurities  in  city  air  shows 
that  a  large  percentage  of  the  particles  are  carbon. 

CLASSIFICATION   OF   AIR  IMPURITIES 

The  most  conspicuous  sources  of  atmospheric  pollution  may  be  classi- 
fied arbitrarily  according  to  the  size  of  the  particles  as  dusts,  fumes,  and 
smoke.  Dusts  consist  of  particles  of  solid  matter  varying  from  1.0  to  150 
microns  in  size,  (micron  =  0.001  millimeter  or  1/25,000  in.)  Fumes 
t  include  particles  resulting  from  chemical  processing,  combustion,  explo- 
sion, and  distillation,  ranging  from  0.1  to  1.0  micron  in  size.  The  word 
fumes  may  be  applied  also  to  mixtures  of  mists  (liquid  droplets)  and  gases 
as  acid  mists.  Smoke  is  composed  of  fine  soot  or  carbon  particles,  usually 
less  than  0.1  micron  in  size,  which  result  from  incomplete  combustion  of 
carbonaceous  materials,  such  as. coal,  oil,  tar,  and  tobacco.  In  addition 
to  carbon  and  soot,  smoke  contains  unconsumed  hydrocarbon  gases, 
sulphur  dioxide,  carbon  monoxide,  and  other  industrial  gases  capable  of 
injuring  property,  vegetation,  and  health. 

The  lines  of  demarcation  in  these  three  classifications  are  neither  sharp 
nor  positive,  but  the  distinction  is  descriptive  of  the  nature  and  origin  of 
of  the  particles,  and  their  physical  action.  Dusts  settle  without  appre- 
ciable agglomeration,  fumes  tend  to  aggregate,  smoke  to  diffuse.  Particles 
which  approach  the  common  bacteria  in  size — about  1  micron — are 
difficult  to  remove  from  air  and  are  apt  to  remain  in  suspension  unless 
they  can  be  agglomerated  by  artificial  means.  The  term  fly-ash  is  usually 
applied  to  the  microscopic  glassy  spheres  which  form  the  principal  solid 
constituent  of  the  effluent  gases  from  powdered-coal  fired  furnaces. 
Cinders  denote  the  larger  solid  constituents  which  may  be  entrained  by 
furnace  gases. 

It  is  well  established  that  particles  larger  than  about  1  micron  are 
unlikely  to  remain  suspended  in  air  currents  of  moderate  strength.  Only 

79 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 


violent  air  motion  will  sustain  them  in  air  long  enough  for  them  to  be 
breathed.  This  means  that,  in  hygenic  problems,  the  engineer  is  con- 
cerned mostly  with  suspensions  of  particles  comparable  to  the  common 


D!AM. 
OF 
PAR- 
TICLES 

m 

HICW113 

SCALE     OF 
ATMOSPHERIC 
IMPURITIES 

RATE  OF 
SETTLING 
IN  F.PM. 
FOR 
SPHERED 
OF 
DENSITY  I 
AT  10*  F. 

NUMBER 
OFPAR- 
TICIESW 
OMECUFT 

SURFACE 
AREA  IN 
SQUARE 
INCHES 

LAWS  OF  SETTLING 
IN      RELATION    TO 
PARTICLE     SIZE 
(LINES  OF  DEMARCATION   APPRO*.) 

AIR   CONTAINING 
.0006  GRAINS  OF 
IMPURITIES    PER 
CU.FT.(BEM31T<-0 

8000 
600O 

p"  :..  -i."..--.  —  r.,  -td 

|  PARTICLES  SETTLE  WITH  CONSTANT  VELOCITY  | 

PARTICLES      FALL     WITH 
INCREASING     VELOCITY 

4000 
£000 

1000 
800 
600 

400 
200 

100 
SO 

=^=^rz|: 

790 

.075 

.000)65 

C  =  24.9VD«7 

oVelocity  ctn/s«c. 
CWelocity  ft/mm. 

d«Diam  of  par- 
ticle in  cm. 

D*Diam.  of  par- 
ticlt  in  Microns 

r«  Radius  of  par- 
ticle in  cm. 

g-SSlcm/aec* 
acceleration 

s,-  Density  of 
particle 

sz=Density  of  Air 
(Very  Small 
relative  to  s,) 

57*  Viscosity  of 
air  in  poises 
-!814xlO~Tfor 
o.r  at  70*  F. 

(Mean  free 
path  of  gas 
molecules  ) 

'•^^FP- 

^H-J^^^ 

555 

g 

•00_0!3__ 
.003653 

- 

-1 

-L."  S)D  <• 

e*»                  ^,!ui   O: 

75 

3 

A| 

•-f*i 

i  «   ^ 

ff 

iza          ^ 

O            u 

—  r-^r  —  * 

STOKES 
LAW 

FOR  AIR  AT  70  *F. 

c  -300,460s,d* 
C  -.0059ZS.D* 

CUNNINGHAM'S 

60 
40 

20 

10 
8 

3| 

stgss 

^  

tf 

532 

600 
75000 

.0073 

.0365  * 
|&1N.SQ. 

Is 

JGp  3  ij 

" 

^- 

5 

si5"  s  i 

t; 

s 

o* 

1 

^1< 

1 

G 

Z 
1 

-| 

m 

148 
JOT  5" 

600.000 
75X10* 

.073 
.365  3 

3 

tf 

s! 

H  u* 

CE 

| 

a. 

:( 

53  UJ  o 

S 

a 

.6 

.4 

.2 

1 

^^H 

-K 

_£j±jjU 

002=1.4" 

60XI07 

8 
.73 

FACTOR 

ifl 

y 

s 

PCRHR. 
MOtn-64 

75x10* 

3.65  » 

f1"!      « 

ft  S 

2 

< 

C'-C  OF  STOKES  IAW 
K  -.8  TO  .86 

uJ 

UJ 

s  f 

?  k  • 

1 

te. 

ci 

I 

^ 

.01 

PER  HR. 

i.e  IN.SO. 

PARTICLES      N 
GAS       MOL 

BROWN  IAN 
MOVEMENT 

A=Vff    3^7 

1OVE     LIKE 
&CULES 

A-  Distance  of 
motion  m  time  t 

R-Gas  constant 
-0.316x10'' 

T-  Absolute 
Temperature 

N*  Number  of  Gas 
molecules  in 
onemoi-edOSxlO23 



•fii 

-^  — 

Sti 

ri— 

—  & 

0 

73XI011 

UJ 

—  y: 

0 

en 

t 

5 

-a*? 

£s< 

o5 

;    5       « 

hJ 

a|  8     8 

«»• 

15-    f 

o 

.OOI 

0 

60XI013 

73.0 

'-.5    8      j 

—  n 

2 

UZh 

^.<     w        & 

0 

365  S 
2.5350.  FT. 



f 

-y 

irl-y 

-• 

5 

Compiled  by  W.  G.  Frank  and  Copyrighted. 
FIG.  1.    SIZES  AND  CHARACTERISTICS  OF  AIR-BORNE  SOLIDS 

bacteria  in  size.  A  notable  exception  to  this  size  limitation  is  the  common 
hay-fever  producing  pollen  such  as  that  from  rag-weed.  Pollen  grains 
may  be  anything  from  fragments  15  microns  in  diameter  to  whole  pollens 
25  microns  or  more  in  size.  Since  the  lower  limit  of  visability  to  the 


CHAPTER  4.   AIR  POLLUTION 


TABLE  1.    APPROXIMATE  LIMITS  OF  INFLAMMABILITY  OF  SINGLE  GASES  AND  VAPORS 
IN  AIR  AT  ORDINARY  TEMPERATURES  AND  PRESSURES** 


GAS  OR  VAPOR 


LOWER  LIMIT 
VOLTJMB  IN  PER  CENT 


HIGHER  LIMIT 
VOLUME  IN  PER  CENT 


Hydrogen  

4  1 

74  o 

Ammonia  

16  0 

27  0 

Hydrogen  sulphide  

43 

46  0 

Carbon   disulphide 

1  0 

50  0 

Carbon  monoxide  

12  5 

74  0 

Methane  

5  3 

14  0 

Methane  (turbulent  mixture)  

5  0 

15  0 

Ethane  

3  2 

12  5 

Propane- 

2  4 

9  5 

Butane 

19 

85 

Pentane          

1  45 

7  5 

Ethylene 

3  0 

29  0 

Acetylene  -  

3  0 

Acetylene  (turbulent  mixture)  

2  3 

Benzene. 

1  4 

7  0 

Toluene.       

1  4 

7  0 

Cyclohexane 

13 

8  3 

Methyl  cyclohexane  

1  2 

Methyl  alcohoL  

7  0 

Ethyl  alcohol  

4  0 

19  0 

Ethyl  ether._  ..  . 

1  7 

26  0 

Benzine  

1  1 

Gasoline  

1  4 

6  0 

Water  gas 

6  to  9 

55  to  70 

Ethylene  oxide  

3.0 

80  0 

Acetaldehyde  

4  0 

57  0 

Furfural  (125  C)  

2.0 

Acetone 

3  0 

11  0 

Acetone  (turbulent  mixture)  

2.5 

Methyl  ethyl  ketone. 

2  0 

12  0 

Methyl  formate 

6  0 

20  0 

Ethyl  formate  

3  5 

16  5 

Methyl  acetate- 

4  1 

14  0 

Ethyl  acetate  

2  5 

11  5 

Proovl  acetate 

2  0 

Butyl  acetate  (30  C)  

1.7 

Ethyl  nitrite. 

3.0 

Methyl  chloride 

8  0 

19  0 

Methyl  bromide—  ... 

13.5 

14  5 

Ethyl  chloride 

4  0 

15  0 

Ethyl  bromide 

7  0 

11  0 

Ethylene  dichloride 

6  0 

16  0 

Dichlorethylene 

10  0 

13  0 

Vinyl  chloride,  

4.0 

22.0 

Pyridine  (70  C)      

1.8 

12  5 

Natural  gas 

4  8 

13  5 

Illuminating  gas  

5.3 

31  0 

Blast-furnace  eras 

35  0 

74  0 

^Limits  of  Inflammability  of  Gases  and  Vapors,  by  H.  F.  Coward  and  G.  W.  Jones,  (U.  S.  Bureau  < 
Mines,  Bulletin  No.  279,  1931). 


81 


HEATING   VENTILATING  AIR  CONDITIONING  GUIDE  1938 


average  eye  is  around  50  microns  all  air  floated  material  of  this  kind  is  too 
small  to  identify  without  the  aid  of  the  microscope. 

Mineral  particles,  such  as  grains  of  sand,  bits  of  rock,  volcanic  ash,  or 
fly-ash,  can  be  transported  long  distances  under  unusual  circumstances. 
Thus,  the  dust  storms  of  1935  in  the  Kansas  district  resulted  in  vast 
amounts  of  fine  top  soil  being  thrown  high  into  the  air.  Solar  illumination 
as  far  east  as  Boston  was  affected  noticeably  and  particles  as  large  as  40 
to  50  microns  were  actually  carried  half  way  across  the  continent  before 
they  settled  out.  In  similar  manner  volcanic  ash  has  been  carried  even 
further.  It  is  not  surprising,  therefore,  that  fly-ash  from  furnace  gases, 
cement  dust  and  the  like,  can  be  carried  for  considerable  distances  and 
occasionally  the  engineer  is  confronted  with  the  problem  of  removing  such 
material  before  the  air  in  question  is  suitable  for  use  in  building  venti- 
lation. 

The  physical  properties  of  the  particulate  impurities  of  air  are  summar- 
ized conveniently  in  the  chart  of  Fig.  1. 

In  the  case  of  gases  the  physical  property  which  is  probably  of  most 
importance  is  inflammability.  The  best  data  available  at  present  on  this 
subject  are  given  in  Table  1. 

Dust  Concentrations 

It  is  customary  to  report  dust  concentrations  as  grains  per  1000  cu  ft 
or  milligrams  per  cubic  meter.  Gas  concentrations  are  commonly'  re- 
corded as  milligrams  per  cubic  meter  or  as  parts  per  million  or  as  per 
cent  by  volume.  Typical  ranges  in  dust  concentrations  as  now  found  in 
practical  applications  are  given  in  Table  2. 

TABLE  2.    DCST  CONCENTRATION  RANGES  IN  PRACTICAL  APPLICATIONS** 


APPLICATION 

GRAINS  PER  1000  Cn  FT 

MGS  PER  Cu  M 

Rural  and  suburban  districts 

0  2  to    04 

04.  rn  ft  fc 

Metropolitan  districts  

0  4  to    08 

0  9  to  1  8 

Industrial  districts  

0  8  to    15 

1  8  to  3  5 

Dusty  factories  or  mines  

4  0  to  80  0 

10  to  200 

Explosive  concentrations  (as  of  flour  or  soft  coal).. 

4000  to  8000 

10,000  to  20,000 

«1  grain  per  1000  cu  ft  =  2.3  mgs  per  cubic  meter;  1  oz  per  cubic  foot  =*  1  gram  per  liter. 

The  engineer  frequently  desires  information  regarding  the  effects  of 
various  concentrations  of  gases  or  dusts  upon  man,  as  the  success  of  a 
particular  installation  may  depend  upon  the  maintenance  of  air  which  is 
adequately  clean.  At  the  present  time  there  are  a  number  of  organi- 
zations working  on  this  problem  all  of  them  publishing  literature  of 
various  kinds.1  References  to  books  covering  the  hygienic  significance, 
determination  and  control  of  dust  are  listed  at  the  end  of  this  chapter. 


m 
meat  of 


f'  S-P^lic  Health  Service;  Division  of  Labor  Standards,  U.  S.  Depart- 
of  Toronto  Medical  School,  Canada;  Saranac  Laboratories,  Saranac  Lake 
'  In",  ^^S^A  **-  Harvard  ^h001  of  Public  Health!  BoS?,  M£  .\ 
:1  '^  the  Departraents  of  Health  and  °f  Labor  in  the  United  States 


82 


CHAPTER  4.   AIR  POLLUTION 


AIR  POLLUTION  AND  HEALTH 

The  prevention  of  various  diseases  which  result  from  exposure  to 
atmospheric  impurities  is  an  engineering  problem.  It  is  important  for 
the  engineer  to  insure,  by  proper  ventilation,  suitable  environments  for 
working  or  for  general  living.  If  the  equipment  used  is  to  be  successful,  it 
must  operate  automatically  as  in  the  modern  air  conditioned  theatre  or 
railroad  train. 

In  Table  3  are  given  data  on  permissable  concentrations  of  various 
substances,  gases  and  dusts,  which  occur  in  industry.  The  prudent 

TABLE  3.    TOXICITY  OF  GASES  AND  FUMES  IN  PARTS  PER  10,000  PARTS  OF  AiRa 


VAPOR  OB  GAS 

RAPIDLY 
FATAL 

MAXIMUM 
CONCENTRATION 

FOR  FROM 

M  TO  1  HOUR 

\ 

1          MAXIMUM 
CONCENTRATION 
FOR  1  HOUH 

MAXIMUM 
ALLOWABLE 
FOR  PROLONGED 
EXPOSURE 

Carbon  monoxide  
Carbon  dioxide  

40 
800-1000 

15-20 

10 

1 

Hydrocyanic  acid  

30 

\1A 

'"y" 

l.< 

Ammonia 

50-100 

25 

3 

1 

Hydrochloric  acid  gas  

10-20 

Ko 

Chlorine....".  

10 

\s 

Koo 

Hydrofluoric  acid  gas._  

2 

Mo 

3*33 

Sulphur  dioxide.-  

4-5 

M-l 



s^.Q 

Hydrogen  sulphide  

Carbon  bisulphide. 

10-30 

5-7 
11 

2-3 

5 

1 

\4 

Phosphene 

20 

4-6 

1  2 

Arsine  

2H 

1A 

Phosgene 

Over  34 

i/ 

Mnn 

Nitrous  furnes  

2^-7i| 

1-1  H 

7Q 

Benzene             

190 

31-47 

lU-3 

Toluene  and  xylene  

190 

31-47 

Aniline  

1-1^ 

Kn 

Nitrobenzene 

Hoo 

i/ 

44  i\f\ 

Carbon  tetrachloride  
Chloroform 

480 
250 

240 
140 

40 
50 

1 

2 

Tetrachlorethane  _  
Trichlorethylene  

73 
370 

Ho 

Methyl  chloride.....  
Methyl  bromide  

1500-3000 
200-400 

200-400 
20-40 

70 
10 

5-10 
2 

Lead  dust.  

0  15  mg/cu  m 

Quartz  dust 

1  mg/cu  m 

^Adapted  from  Y.  Henderson  and  H.  Haggard.    (See  ^oxtows  Gases,  1927,  and  Lessotw  Learned  from 
Industrial  Gases  and  Fumes,  Institute  of  Chemistry  of  Great  Britain  and  Ireland,  London,  1930.) 

engineer  will  design  equipment  using  these  bench  marks  as  the  upper 
limits  of  pollution.  In  general  it  is  good  practice  to  avoid  recirculation 
of  air  which  contains  originally  toxic  substances.  Obviously  there  may  be 
exceptions  to  this  rule,  but  it  is  one  which  is  generally  being  followed  in 
current  practice. 

'  Bronchitis  is  the  chief  condition  associated  with  exposure  to  thick  dust, 
and  follows  upon  inhalation  of  practically  any  kind  of  insoluble  and  non- 
colloidal  dust.  Atmospheric  dust  in  itself  cannot  be  blamed  for  causing 
tuberculosis,  but  it  may  aggravate  the  disease  once  it  has  started.2 


'Physiological  Response  of  the  Peritoneal  Tissue  to  Dusts  Introduced  as  Foreign  Bodies,  by  Miller 
and  Sayers  (U.  S.  Public  Health  Reports,  49:80,  1934). 

83 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

The  sulphurous  fumes  and  tarry  matter  in  smoke  are  more  dangerous 
than  the  carbon.  In  foggy  weather  the  accumulation  of  these  substances 
in  the  lower  strata  may  be  such  as  to  cause  irritation  of  the  eyes,  nose,  and 
respiratory  passages,  leading  to  asthmatic  breathing  and  bronchitis  and, 
in  extreme  cases,  to  death.  The  Meuse  Valley  fog  disaster  will  probably 
become  a  classic  example  in  the  history  of  gaseous  air  pollution.  Re- 
leased  in  a  rare  combination  of  atmospheric  calm  and  dense  ^fog,  it^is 
believed  that  sulphur  dioxide  and  other  toxic  gases  from  the  industrial 
region  of  the  valley  caused  63  sudden  deaths,  and  injuries  to  several 
hundred  persons. 

Carbon  monoxide  from  automobiles  and  from  chimney  ^  gases  consti- 
tutes another  important  source  of  aerial  pollution  in  busy  cities.  During 
heavy  traffic  hours  and  under  atmospheric  conditions  favorable  to  con- 
centration, the  air  of  congested  streets  is  found  to  contain  enough  CO  to 
menace  the  health  of  those  exposed  over  a  period  of  several  hours,  par- 
ticularly if  their  activities  call  for  deep  and  rapid  breathing.^  In  open  air 
under  ordinary  conditions  the  concentration  of  CO  in  city  air  is  insufficient 
to  affect  the  average  city  dweller  or  pedestrian. 

Occlusion  of  Solar  Radiation 

The  loss  of  light,  particularly  the  occlusion  of  solar  ultra-violet  light 
due  to  smoke  and  soot,  is  beginning  to  be  recognized  as  a  health  problem 
in  many  industrial  cities.  Measurements  of  solar  radiation  in  Baltimore3 
by  actinic  methods  show  that  the  ultra-violet  light  in  the  country  was 
50  per  cent  greater  than  in  the  city.  In  New  York  City4  a  loss  as  great  as 
50  per  cent  in  visible  light  was  found  by  the  photo-electric  cell  method. 

Recent  studies5  in  Pittsburgh  indicate  that  heavy  smoke  pollution  is 
definitely  unhealthful.  Heretofore  adequate  proofs  on  this  point  were 
lacking. 

The  aesthetic  and  economic  objections  to  air  pollution  are  so  definite, 
and  the  effect  of  air-borne  pollen  can  be  shown  so  readily  as  the  cause  of 
hay  fever  and  other  allergic  diseases,  that  means  and  expenses  of  pre- 
vention or  elimination  of  this  pollution  are  justified. 

SMOKE  AND  AIR  POLLUTION  ABATEMENT 

Successful  abatement  of  atmospheric  pollution  requires  the  combined 
efforts  of  the  combustion  engineer,  the  public  health  officer,  and  the 
public  itself.  The  complete  electrification  of  industry  and  railroads,  and 
the  separation  of  industrial  and  residential  communities  would  aid 
materially  in  the  effective  solution  of  the  problem. 

In  the  large  cities  where  the  nuisance  from  smoke,  dust  and  cinders  is 
the  most  serious,  limited  areas  obtain  some  relief  by  the  use  of  district 
heating.  The  boilers  in  these  plants  are  of  large  size  designed  and  oper- 
ated to  burn  the  fuel  without  smoke,  and  some  of  them  are  equipped  with 
dust  catching  devices.  The  gases  of  combustion  are  usually  discharged  at 


'Effects  of  Atmospheric  Pollution  Upon  Incidence  of  Solar  Ultra-Violet  Light,  by  J.  H.  Shrader,  M.  H. 
Coblentz  and  F.  A.  Korff  (American  Journal  of  Public  Health,  p.  7,  Vol.  19,  1929). 

'Studies  in  Illumination,  by  J.  E.  Ives  (U.  S.  Public  Health  Service  Bulletin  No.  197,  1930). 

'Pneumoconiosis  in  the  Pittsburgh  district,  Based  on  a  Study  of  2,500  Post  Mortem  Examinations 
made  in  Pittsburgh  Hospitals,  by  Schnurer  et  al  (Journal  Industrial  Hygiene,  17:294,  March,  1935). 

84 


CHAPTER  4.    AIR  POLLUTION 


a  much  higher  level  than  is  possible  in  the  case  of  buildings  that  operate 
their  own  boiler  plants. 

In  general,  time,  temperature  and  turbulence  are  the  essential  require- 
ments for  smokeless  combustion.  Anything  that  can  be  done  to  increase 
any  one  of  these  factors  will  reduce  the  quantity  of  smoke  discharged. 
Especial  care  must  be  taken  in  hand-firing  bituminous  coals.  (See 
Chapter  9.) 

Checker  or  alternate  firing,  in  which  the  fuel  is  fired  alternately  on 
separate  parts  of  the  grate >  maintains  a  higher  furnace  temperature  and 
thereby  decreases  the  amount  of  smoke. 

Coking  and  firing,  in  which  the  fuel  is  first  fired  close  to  the  firing  door 
and  the  coke  pushed  back  into  the  furnace  just  before  firing  again,  pro- 
duces the  same  effect.  The  volatiles  as  they  are  distilled  thus  have  to 
pass  over  the  hot  fuel  bed  where  they  will  be  burned  if  they  are  mixed  with 
sufficient  air  and  are  not  cooled  too  quickly  by  the  heat-absorbing  surfaces 
of  the  boiler. 

Steam  or  compressed  air  jetst  admitted  over  the  fire,  create  turbulence 
in  the  furnace  and  bring  the  volatiles  of  the  fuel  more  quickly  into  contact 
with  the  air  required  for  combustion.  These  jets  are  especially  helpful 
for  the  first  few  minutes  after  each  firing.  Frequent  firings  of  small 
charges  shorten  the  smoking  period  and  reduce  the  density.  Thinner 
fuel  beds  on  the  grate  increase  the  effective  combustion  space  in  the 
furnace,  supply  more  air  for  combustion,  and  are  sometimes  effective  in 
reducing  the  smoke  emitted,  but  care  should  be  taken  that  holes  are  not 
formed  in  the  fire.  A  lower  volatile  coal  or  a  higher  gravity  oil  always 
produces  less  smoke  than  a  high  volatile  coal  or  low  gravity  oil  used  in 
the  same  furnace  and  fired  in  the  same  manner. 

The  installation  of  more  modern  or  better  designed  fuel  burning  equip- 
ment, or  a  change  in  the  construction  of  the  furnace,  will  often  reduce 
smoke.  The  installation  of  a  Dutch  oven  which  will  increase  the  furnace 
volume  and  raise  the  furnace  temperature  often  produces  satisfactory- 
results. 

In  the  case  of  new  installations,  the  problem  of  smoke  abatement  can 
be  solved  by  the  selection  of  the  proper  fuel-burning  equipment  and 
furnace  design  for  the  particular  fuel  to  be  burned  and  by  the  proper 
operation  of  that  equipment.  Constant  vigilance  is  necessary  to  make 
certain  that  the  equipment  is  properly  operated.  In  old  installations  the 
solution  of  the  problem  presents  many  difficulties,  and  a  considerable 
investment  in  special  apparatus  is  necessary. 

Legislative  measures  at  the  present  time  are  largely  concerned  with  the 
smoke  discharged  from  the  chimneys  of  boiler  plants.  Practically  all  of 
the  ordinances  limit  the  number  of  minutes  in  any  one  hour  that  smoke  of 
a  specified  density,  as  measured  by  comparison  with  a  Ringelmann  Chart 
(Chapter  44),  may  be  discharged. 

These  ordinances  do  not  cover  the  smoke  discharged  at  low  levels  by 
automobiles,  and,  although  they  have  been  instrumental  in  reducing  the 
smoke  emitted  by  boiler  plants,  they  have,  in  many  instances,  increased 
the  output  of  chimney  dust  and  cinders  due  to  the  use  of  more  excess  air 
and  to  greater  turbulence  in  the  furnaces. 

Legislative  measures  in  general  have  not  as  yet  covered  the  noxious 

85 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 

gases,  such  as  sulphur  dioxide  and  sulphuric  acid  mist,  which  are  dis- 
charged with  the  gases  of  combustion.  ^  Where  high  sulphur  coals  are 
burned,  these  sulphur  gases  present  a  serious  problem. 

DUST  AND  CINDERS 

The  impurities  in  the  air  other  than  smoke  come  from  so  many  sources 
that  they  are  difficult  to  control.  Only  those  which  are  produced  in 
large  quantities  at  a  comparatively  few  points,  such  as  the  dust,  cinders 
and  fly-ash  discharged  to  the  atmosphere  along  with  the  gases  of  com- 
bustion from  burning  solid  fuel,  can  be  readily  controlled. 

Dusts  and  cinders  in  flue  gas  may  be  caught  by  various  devices  on  the 
market,  such  as  fabric  filters,  dust  traps,  settling  chambers,  centrifugal 
separators,  electrical  precipitators,  and  gas  scrubbers,  described  in 
Chapter  26. 

The  cinder  particles  are  usually  larger  in  size  than  the  dust  particles; 
they  are  gray  or  black  in  color,  and  are  abrasive.  Being  of  a  larger  size, 
the  range  within  which  they  may  annoy  is  limited. 

The  dust  particles  are  usually  extremely  fine;  they  are  light  gray  or 
yellow  in  color,  and  are  not  as  abrasive  as  cinder  particles.  Being  ex- 
tremely fine,  they  are  readily  distributed  over  a  large  area  by  air  currents. 

The  nuisance  created  by  the  solid  particles  in  the  air  is  dependent  on 
the  size  and  physical  characteristics  of  the  individual  particles.  The 
difficulty  of  catching  the  dust  and  cinder  particles  is  principally  a  function 
of  the  size  and  specific  gravity  of  the  particles. 

Lower  rates  of  combustion  per  square  foot  of  grate  area  will  reduce  the 
quantity  of  solid  matter  discharged  from  the  chimney  with  the  gases  of 
combustion.  The  burning  of  coke,  coking  coal,  and  sized  coal  from  which 
the  extremely  fine  coal  has  been  removed  will  not  as  a  general  rule  produce 
as  much  dust  and  cinders  as  will  result  from  the  burning  of  non-coking 
coals  and  slack  coal  when  they  are  burned  on  a  grate. 

Modern  boiler  installations  are  usually  designed  for  high  capacity  per 
square  foot  of  ground  area  because  such  designs  give  the  lowest  cost  of 
construction  per  unit  of  capacity.  Designs  of  this  type  discharge  a 
large  quantity  of  dust  and  cinders  with  the  gases  of  combustion,  and  if 
pollution  of  the  atmosphere  is  to  be  prevented,  some  type  of  catcher  must 
be  installed. 

NATURE'S  DUST   CATCHER 

Nature  has  provided  means  for  catching  solid  particles  in  the  air  and 
depositing  them  upon  the  earth.  A  dust  particle  forms  the  nucleus  for 
each  rain  drop  and  the  rain  picks  up  dust  as  it  falls  from  the  clouds  to  the 
earth.  In  fact,  without  dust  in  the  air  to  form  the  nuclei  for  rain  drops  it 
would  never  rain,  and  the  earth  would  be  continually  enveloped  in  a 
cloud  of  vapor.  However,  it  was  found  in  recent  studies6  that  rain  was 
not  a  good  air  cleaner  of  the  material  below  about  0.7  micron. 


•Atmospheric  Pollution  of  American  Cities  for  the  years  1931-1933,  by  J.  E.  Ives  et  al  (U.  5.  Public 
Health  Bulletin  No*  224.  March,  1936). 


CHAPTER  4.   AIR  POU.UTION 


REFERENCES 

Bulletin,  Air  Hygiene  Foundation,  Inc.,  Pittsburgh,  Pa. 

Determination  and  Control  of  Industrial  Dust,  by  J.  J.  Bloomfield  and  J.  M.  Dalla 
Valle  (U.  S.  Public  Health  Bulletin,  No,  217,  1935).' 

Journal  of  Industrial  Hygiene  and  Toxicology,  Harvard  School  of  Public  Health, 
Boston,  Mass. 

Reports  of  the  National  Silicosis  Conference,  Washington,  D.  C.  To  be  published 
by  the  U.  S.  Department  of  Labor. 

Saranac  Symposium  on  Silicosis,  1937,  Saranac  Laboratories,  Saranac,  N.  Y. 

Industrial  Dust,  by  Philip  Drinker  and  Theodore  Hatch,  McGraw  Hill  Co.,  N.  Y. 

Noxious  Gases,  by  Y.  Henderson  and  H.  Haggard,  Chemical  Catalog  Co.,  N.  Y. 

Occupation  and  Health,  International  Labour  Office. 

Preventive  Medicine  and  Hygiene,  by  Milton  J.  Rosenau,  D.  Appleton- Century 
Co.,  N.  Y. 


PROBLEMS  IN  PRACTICE 

1  •  Classify  the  detrimental  aspects  of  air  pollution  as  it  affects  large  industrial 
communities. 

Air  pollution  may  be  classified  (a)  medical,  as  it  affects  the  physiological  functions  of 
people;  (b)  botanical,  as  it  affects  vegetation,  trees,  plants,  shrubs  and  flowers;  and  (c) 
physical,  as  it  affects  the  discoloration  and  deterioration  of  buildings,  and  the  nuisance 
of  soiled  interior  furnishings,  clothes,  merchandise,  etc. 

2  •  Distinguish  between  dusts,  fumes,  and  smokes. 

Solid  particles  ranging  in  size  from  1.0  micron  to  150  microns  are  called  dusts  (micron  = 
Ms. ooo  in.)- 

Particles  resulting  from  sundry  chemical  reactions  and  ranging  from  0.1  to  1.0  micron  in 
size  are  called  fumes. 

Carbon  particles  less  than  0.1  micron  in  size  which  generally  arise  from  the  incomplete 
combustion  of  such  materials  as  coal,  oil,  or  tobacco  are  called  smokes, 

3  •  What  are  some  of  the  more  important  physical  properties  of  these  various 
groups  of  foreign  bodies  which  are  of  importance  in  ventilation? 

In  slowly  moving  air,  dusts  tend  to  settle  out  by  gravity  without  agglomerating  to  form 
larger  particles;  fumes  have  the  tendency  to  form  larger  particles  which  will  settle  when 
they  attain  the  size  of  approximately  1.0  micron;  while  smokes  tend  to  diffuse  and  remain 
in  the  air  as  permanent  impurities. 

4  •  Why  is  atmospheric  pollution  an  important  engineering  problem? 

a.  Certain  impurities,  when  present  in  too  great  concentrations,  cause  ill  health  or  even 
death. 

b.  High  concentrations  of  solids  occlude  solar  radiations. 

c.  Some  materials  cause  permanent  injury  to  parts  of  buildings,  as  sulphur  fumes  corrode 
exposed  metal. 

d.  Extra  cleaning  expense  is  incurred  in  dusty  localities. 

e.  Internal  combustion  engines  are  damaged  by  abrasive  dusts. 

5  •  How  may  the  hazards  of  dust-producing  industrial   operations   best  be 
curtailed? 

By  providing  mechanical  exhaust  ventilation  sufficient  to  keep  dust  concentration  at  a 
safe  level  (see  Table  3)  and  then  removing  foreign  bodies  to  reduce  the  pollution  of  out- 
side air. 

87 


HEATING  VENTILATING   AIR  CONDITIONING   GUIDE  1938 

6  •  How  may  the  pollution  of  the  atmosphere  he  lessened? 

By  compelling  industrial  plants  to  install  dust  catching  and  smoke  controlling  devices. 
In  many  cities  the  domestic  heating  plant  is  one  of  the  most  serious  offenders,  but  these 
plants  are  too  small  to  justify  the  installation  of  dust  catchers.  Public  education  in 
improved  firing  methods  would  be  of  considerable  help  in  this  field. 

7  •  What  size  particles  are  detrimental  to  health? 

While  fairly  large  particles  may  enter  the  upper  air  passages,  those  found  in  the  lungs 
are  seldom  more  than  10  microns  in  size,  and  comparatively  few  of  them  are  more  than 
5  microns.  It  is  agreed  that  particles  between  %  and  2  microns  may  be  harmful;  some 
authorities  place  the  upper  limit  at  about  5  microns,  and  some  incline  to  extend  the 
lower  limit  to  0.1  of  a  micron. 

8  •  Is  the  shape  of  the  particle  of  any  significance? 

Hard  particles  with  sharp  corners  or  edges  have  a  cutting  effect  on  the  delicate  mucous 
membranes  of  the  upper  respiratory  tract  which  may  lower  the  resistance  of  the  nose  and 
throat  to  acute  infections.  This  is  aggravated  by  the  irritating  effects  of  some  chemical 
compounds  which  may  be  taken  in  with  the  air  and  which  act  to  reduce  resistance. 

9  •  What  are  the  principal  meteorological  effects  of  smoke  and  dust? 

a.  The  reduction  in  the  amount  of  light  received.  Measurements  have  shown  that 
visible  light  may  be  as  much  as  50  per  cent  less  intense  in  a  smoky  section  of  a  city  than 
in  a  section  that  is  free  from  smoke.  Ultra-violet  light  is  reduced  as  much  or  more,  and 
in  some  cases  is  cut  out  entirely  for  a  time. 

6.  Smoke  and  dust  aid  in  the  formation  and  prolongation  of  fogs.  City  fogs  accumulate 
smoke  and  become  darker  in  color  and  very  objectionable.  The  sun  requires  a  longer 
time  to  disperse  them,  and  when  the  water  is  evaporated,  there  is  a  rain  of  smoke  and 
soot  particles  that  have  been  entrained. 

10  •  Why  has  not  smoke  abatement  been  more  effective? 

Because  communities  have  not  been  made  sufficiently  aware  of  the  possibilities  of 
burning  high  volatile  fuels  smokelessly  and  of  separating  cinder  and  ash  from  the  stack 
gases  to  a  degree  that  will  prevent  a  nuisance. 

11  •  Is  the  abatement  of  dust  and  cinders  important? 

Yes.  Only  a  small  percentage  of  the  solid  emission  from  stacks  is  smoke,  in  the  accepted 
popular  sense;  the  remainder  is  fly-ash  and  cinders.  While  black  smoke  is  disagreeable 
and  its  tarry  matter  and  carbon  particles  soil  anything  with  which  they  come  in  contact, 
the  cinders  and  some  of  the  ash  are  hard  and  destructive.  They  also,  together  with 
dusts  from  industrial  processes,  make  up  the  irritating,  air-borne  solids  that  are  breathed 
by  individuals  not  working  in  a  dusty  mill  or  factory. 

12  •  Are  air-borne  impurities  causative  factors  in  hay  fever,  bronchial  asthma, 
and  allergic  disorders? 

Yes.  Recent  medical  investigations  indicate  that  90  per  cent  of  seasonal  hay  fever  and 
40  per  cent  of  bronchial  asthma  are  caused  by  air-borne  pollens,  tree  dusts,  and  other 
allergic  irritants. 

13  •  Name  some  essential  requirements  for  the  smokeless  combustion  of  fuels. 

Time,  temperature,  and  turbulence.  A  study  of  these  factors  is  usually  of  value  in 
overcoming  a  smoke  nuisance. 

14  •  What  is  the  Ringelmann  Chart  Method  of  comparing  smoke  densities? 

See  Chapter  44.  The  Ringelmann  Chart  consists  of  four  cards  ruled  with  lines  having 
different  degrees  of  blackness.  These  cards,  together  with  a  white  card  and  a  black  one, 
are^hung  in  a  horizontal  row  50  ft  from  the  observer.  At  this  distance  the  lines  become 
invisible  and  the  cards  appear  to  be  different  shades  of  gray,  ranging  from  white  to  black. 
The  observer,  by  matching  the  cards  against  the  shades  of  smoke  coming  from  a  stack,  is 
able  to  estimate  the  blackness  of  the  smoke  as  compared  with  the  chart. 

88 


Chapter  5 

HEAT  TRANSMISSION  COEFFICIENTS 
AND  TABLES 

Methods  o£  Heat  Transfer,  Coefficients,  Conductivity  of 
Homogeneous  Materials,  Surface  Conductance  Coefficients, 
Air  Space  Conductance,  Practical  Coefficients,  Table  of  Con- 
ductivities and  Conductances,  Tables  of  Over- all  Coefficients 
of  Heat  Transfer  for  Typical  Building  Construction,  Combined 
Coefficients  of  Transmission 

IN  order  to  maintain  comfortable  living  temperatures  within  a  building 
it  is  necessary  to  supply  heat  at  the  same  rate  that  it  is  lost  from  the 
building.  The  loss  of  heat  occurs  in  two  ways,  by  direct  transmission 
through  the  various  parts  of  the  structure  and  by  air  leakage  or  filtration 
between  the  inside  and  outside  of  the  building.  The  purpose  of  this 
chapter  is  to  show  methods  of  calculation  and  to  give  practical  trans- 
mission coefficients  which  may  be  applied  to  various  structures  to  deter- 
mine the  heat  loss  by  direct  transmission.  The  amount  lost  by  air 
nitration  is  determined  by  different  methods,  as  outlined  in  Chapter  6, 
and  must  be  added  to  that  lost  by  direct  transmission  to  obtain  the  total 
heating  plant  requirements. 

METHODS  OF  HEAT  TRANSFER 

Heat  transmission  between  the  air  on  the  two  sides  of  a  structure  takes 
place  by  three  methods,  namely,  radiation,  convection  and  conduction. 
In  a  simple  wall  built  up  of  two  layers  of  homogeneous  materials  separated 
to  give  an  air  space  between  them,  heat  will  be  received  from  the  high 
temperature  surface  by  radiation,  convection  and  conduction.  It  will 
then  be  conducted  through  the  homogeneous  interior  section  by  con- 
duction and  carried  across  to  the  opposite  surface  of  the  air  space  by 
radiation,  conduction  and  convection.  From  here  it  will  be  carried  by 
conduction  through  to  the  outer  surface  and  leave  the  outer  surface  by 
radiation,  convection  and  conduction.  The  process  of  heat  transfer 
through  a  built-up  wall  section  is  complicated  in  theory,  but  in  practice 
it  is  simplified  by  dividing  a  wall  into  its  component  parts  and  considering 
the  transmission  through  each  part  separately.  Thus  the  average  wall 
may  be  divided  into  external  surfaces,  homogeneous  materials  and  interior 
air  spaces.  Practical  heat  transmission  coefficients  may  be  derived  which 
will  give  the  total  heat  transferred  by  radiation,  conduction  and  convec- 
tion through  any  of  these  component  parts  and  if  the  selection  and  method 
of  applying  these  individual  coefficients  is  thoroughly  understood  it  is 
usually  a  comparatively  simple  matter  to  calculate  the  over-all  heat 
transmission  coefficient  for  any  combination  of  materials. 

89 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


HEAT  TRANSFER  COEFFICIENTS 

The  symbols  representing  the  various  coefficients  of  heat  transmission 
and  their  definitions  are  as  follows : 

U  =  thermal^  transmittance  or  over-all  coefficient  of  heat  transmission ;  the  amount  of 
heat  expressed  in  Btu  transmitted  in  one  hour  per  square  foot  of  the  wall,  floor,  roof  or 
ceiling  for  a  difference  in  temperature  of  1  deg  F  between  the  air  on  the  inside  and  that 
on  the  outside  of  the  wall,  floor,  roof  or  ceiling. 

k  =  thermal  conductivity;  the  amount  of  heat  expressed  in  Btu  transmitted  in  one 
hour  through  1  sq  ft  of  a  homogeneous  material  1  in.  thick  for  a  difference  in  temperature 
of  1  deg  F  between  the  two  surfaces  of  the  material.  The  conductivity  of  any  material 
depends  on  the  structure  of  the  material  and  its  density.  Heavy  or  dense  materials,  the 
weight  of  which  per  cubic  foot  is  high,  usually  transmit  more  heat  than  light  or  less  dense 
materials,  the  weight  of  which  per  cubic  foot  is  low. 

C  =  thermal  conductance;  the  amount  of  heat  expressed  in  Btu  transmitted  in  one 
hour  through  1  sq  ft  of  a  non-homogeneous  material  for  the  thickness  or  type  under 
consideration  for  a  difference  in  temperature  of  1  deg  F  between  the  two  surfaces  of  the 
material.  Conductance  is  usually  used  to  designate  the  heat  transmitted  through  such 
heterogeneous  materials  as  plaster  board  and  hollow  clay  tile. 

/  =•  film  or  surface  conductance;  the  amount  of  heat  expressed  in  Btu  transmitted  by 
radiation,  conduction  and  convection  from  a  surface  to  the  air  surrounding  it,  or  vice 
versa,  in  one  hour  per  square  foot  of  the  surface  for  a  difference  in  temperature  of  1  deg  F 
between  the  surface  and  the  surrounding  air.  To  differentiate  between  inside  and  outside 
wall  (or  floor,  roof  or  ceiling)  surfaces,  fi  is  used  to  designate  the  inside  film  or  surface 
conductance  and  /0  the  outside  film  or  surface  conductance. 

a  —  thermal  conductance  of  an  air  space;  the  amount  of  heat  expressed  in  Btu  trans- 
mitted by  radiation,  conduction  and  convection  in  one  hour  through  an  area  of  1  sq  ft  of 
an  air  space  for  a  temperature  difference  of  1  deg  F.  The  conductance  of  an  air  space 
depends  on  the  mean  absolute  temperature,  the  width,  the  position  and  the  character  of 
the  materials  enclosing  it. 

R  —  resistance  or  resistivity  which  is  the  reciprocal  of  transmission,  conductance, 
or  conductivity,  i.e.: 

-jj-  -  over-all  or  air-to-air  resistance. 
-T~  =  internal  resistivity. 

TT  —  internal  resistance, 
c/ 

-j-  —  film  or  surface  resistance. 

1 
—  =  air-space  resistance. 

As  an  example  in  the  application  of  these  coefficients  assume  a  wall 
with  over-all  coefficient  U.  Then, 

H  =  AU(t-to)  (1) 

where 

H  =  Btu  per  hour  transmitted  through  the  material  of  the  wall,  glass,  roof  or 
floor. 

A  *  area  in  square  feet  of  wall,  glass,  roof,  floor,  or  material,  taken  from  building 
plans  or  actually  measured.  (Use  the  net  inside  or  heated  surface  dimensions 
in  all  cases.) 

-  k  =  temperature  difference  between  inside  and  outside  air,  in  which  t  must  always 
be  taken  at  the  proper  level.    Note  that  t  may  not  be  the  breathing-line 


90 


CHAPTER  5.   HEAT  TRANSMISSION  COEFFICIENTS  AND  TABLES 

If  the  heat  transfer  between  the  air  and  the  inside  surface  of  the  wall 
is  being  considered,  then, 

H  =  A  fi  (t  -  h)  f2) 

where 

fi  =  inside  surface  conductance. 

t  and  h  =  the  temperatures  of  the  inside  air  and  the  inside  surface  of  the  wall  re- 
spectively. 

In  practice  it  is  usually  the  over-all  heat  transmission  coefficient  that  is 
required.  This  may  be  determined  by  a  test  of  the  complete  wall,  or 
it  may  be  obtained  from  the  individual  coefficients  by  calculation.  The 
simplest  method  of  combining  the  coefficients  for  the  individual  parts  of 
the  wall  is  to  use  the  reciprocals  of  the  coefficients  and  treat  them  as 
resistance  units.  The  total  over-all  resistance  of  a  wall  is  equal  numeri- 
cally to  the  sum  of  the  resistances  of  the  various  parts,  and  the  reciprocal 
of  the  over-all  resistance  is  likewise  the  over-all  heat  transmission  coef- 
ficient of  the  wall.  For  a  wall  built  up  of  a  single  homogeneous  material 
of  conductivity  k  and  x  inches  thick  the  over-all  resistance, 


If  the  coefficients  /i,/0  and  k,  together  with  the  thickness  of  the  material 
x  are  known,  the  over-all  coefficient  U  may  be  readily  calculated  as  the 
reciprocal  of  the  total  heat  resistance. 

For  a  compound  wall  built  up  of  three  homogeneous  materials  having 
conductivities  AI,  &2  and  ks  and  thicknesses  xi,  xz  and  x$  respectively,  and 
laid  together  without  air  spaces,  the  total  resistance, 

l=!+i+t+t+i 

For  a  wall  with  air  space  construction  consisting  of  two  homogeneous 
materials  of  thicknesses  Xi  and  x2  and  conductivities  ki  and  kz,  respectively, 
separated  to  form  an  air  space  of  conductance  a,  the  over-all  resistance, 

-L  -  —  4-  -5-  4-—+  -5-4-    1        '  m 

U    '    fi   +    ft,    +   a   +    k,  +  7T  5 

Likewise  any  combination  of  homogeneous  materials  and  air  spaces  can 
be  put  into  the  wall  and  the  over-all  resistance  of  the  combination  may  be 
calculated  by  adding  the  resistances  of  the  individual  sections  of  the  wall. 
In  certain  special  forms  of  construction  such  as  tile  with  irregular  air 
spaces  it  is  necessary  to  consider  the  conductance  C  of  the  unit  as  built 
instead  of  the  unit  conductivity  k,  and  the  resistance  of  the  section  is 

equal  to  -pr.    The  method  of  calculating  the  over-all  heat  transmission 
o 

coefficient  for  a  given  wall  is  comparatively  simple,  but  the  selection  of 
the  proper  coefficients  is  often  complicated.  In  some  cases  the  construc- 
tion of  the  wall  is  such  that  the  substituting  of  coefficients  in  the  accepted 
formula  will  give  erroneous  results.  This  is  the  case  with  irregular  cored 

91 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 

out  air  spaces  in  concrete  and  tile  blocks,  and  walls  in  which  there  are 
parallel  paths  for  heat  flow  through  materials  having  different  heat 
resistances.  In  such  cases  it  is  necessary  to  resort  to  test  methods  to 
check  the  calculations,  and  in  practically  all  cases  it  has  been  necessary 
to  determine  fundamental  coefficients  by  test  methods. 

Conductivity  of  Homogeneous  Materials 

The  thermal  conductivity  of  homogeneous  materials  is  affected  by 
several  factors.  Among  these  are  the  density  of  the  material,  the  amount 
of  moisture  present,  the  mean  temperature  at  which  the  coefficient  is 
determined,  and  for  fiberous  materials  the  arrangement  of  fiber  in  the 
material.  There  are  many  fiberous  materials  used  in  building  construc- 
tion and  considered  as  homogeneous  for  the  purpose  of  calculation, 
whereas  they  are  not  really  homogeneous  but  are  merely  considered  so  as  a 
matter  of  convenience.  In  general,  the  thermal  conductivity  of  a  material 
increases  directly  with  the  density  of  the  material,  increases  with  the 
amount  of  moisture  present,  and  increases  with  the  mean  temperature  at 
which  the  coefficient  is  determined.  The  rate  of  increase  for  these  various 
factors  is  not  the  same  for  all  materials,  and  in  assigning  proper  coef- 
ficients one  should  make  certain  that  they  apply  for  the  conditions  under 
which  the  material  is  to  be  used  in  a  wall.  Failure  to  do  this  may  result 
in  serious  errors  in  the  final  coefficients. 

Surface  Conductance  Coefficients 

Heat  is  transmitted  to  or  from  the  surface  of  a  wall  by  a  combination 
of  radiation,  convection  and  conduction.  The  coefficient  will  be  effected 
by  any  factor  which  has  an  influence  on  any  one  of  these  three  methods  of 
transfer.  The  amount  of  heat  by  radiation  is  controlled  by  the  character 
of  the  surface  and  the  temperature  difference  between  it  and  the  sur- 
rounding objects.  The  amount  of  heat  by  conduction  and  convection  is 
controlled  largely  by  the  roughness  of  the  surface,  by  the  air  movement 
over  the  surface  and  by  the  temperature  difference  between  the  air  and 
the  surface.  Because  of  these  variables  the  surface  coefficients  may  be 
subject  to  wide  fluctuations  for  different  materials  and  different  con- 
ditions. The  inside  and  outside  coefficients  jfi  and/0  are  in  general  affected 
to  the  same  extent  by  these  various  factors  and  test  coefficients  deter- 
mined for  inside  surfaces  will  apply  equally  well  to  outside  surfaces  under 
like  conditions.  Values  for  /i  in  still  and  moving  air  at  different  mean 
temperatures  have  been  determined  for  various  building  materials  at  the 
University  of  Minnesota  under  a  cooperative  agreement  with  the  Society.1 

The  relation  obtained  between  surface  conductances  for  different 
materials  at  mean  temperatures  of  20  F  is  shown  in  Fig.  1.  These  values 
were  obtained  with  air  flow  parallel  to  the  surface  and  from  other  tests  in 
which  the  angle  of  incident  between  the  direction  of  air  flow  and  the 
surface  was  varied  from  zero  to  90  deg  it  would  appear  that  these  values 
might  be  lowered  approximately  15  per  cent  for  average  conditions. 
While  for  average  building  materials  there  is  a  difference  due  to  mean 
temperature,  the  greatest  variation  in  these  coefficients  is  caused  by  the 
character  of  the  surface  and  the  wind  velocity.  If  other  surfaces,  such  as 

'Surface  Conductances  as  Affected  by  Air  Velocity,  Temperature  and  Character  of  Surface,  by  F.  B. 
Rowley,  A.  B.  Algren  and  J.  L.  Blackshaw  (A.S.H.V.E.  TRANSACTIONS,  Vol.  36,  1930,  p.  429). 

92 


CHAPTER  5.   HEAT  TRANSMISSION  COEFFICIENTS  AND  TABLES 

aluminum  foil  with  low  emissivity  coefficients  were  substituted,  a  large 
part  of  the  radiant  heat  would  be  eliminated.  This  would  reduce  the 
total  coefficient  for  all  wind  velocities  by  about  0.7  Btu  and  would  make 
but  very  little  difference  for  the  higher  wind  velocities.  In  many  cases  in 
building  construction  the  heat  resistance  of  the  internal  parts  of  the  wall 
is  high  as  compared  with  the  surface  resistance  and  the  surface  factors 
become  of  small  importance.  In  other  cases  such  as  single  glass  windows 
the  surface  resistances  constitute  practically  the  entire  resistance  of  the 
structure^  and  therefore  become  important  factors.  Due  to  the  wide 
variation  in  surface  coefficients  for  different  conditions  their  selection  for 


15  20  25 

AIR  VELOCITY,  M.  P.  H. 

FIG.  1.    CURVES  SHOWING  RELATION  BETWEEN  SURFACE  CONDUCTANCES  FOR 
DIFFERENT  SURFACES  AT  20  F  MEAN  TEMPERATURE 

a  practical  building  becomes  a  matter  of  judgment.  In  calculating  the 
over-all  coefficients  for  the  walls  of  Tables  3  to  12,  1.65  has  been  selected 
as  an  average  inside  coefficient  and  6.0  as  an  average  outside  coefficient 
for  a  15-mile  wind  velocity.  In  special  cases  where  surface  coefficients 
become  important  factors  in  the  over-all  rate  of  heat  transfer  more 
selective  coefficients  may  be  required, 

Air  Space  Conductance 

Heat  is  conducted  across  an  air  space  by  a  combination  of  radiation, 
conduction  and  convection.  The  amount  of  heat  by  radiation  is  governed 
largely  by  the  nature  of  the  surface  and  the  temperature  difference 
between  the  boundary  surfaces  of  the  air  space.  Conduction  and  con- 

93 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 

vection  are  controlled  largely  by  the  width  and  shape  of  the  air  space  and 
the  roughness  of  the  boundary  surfaces.  The  thermal  resistances  of  air 
spaces  bounded  by  extended  parallel  surfaces  perpendicular  to  the 
direction  of  heat  flow  and  at  different  mean  temperatures  have  been 
determined  for  average  building  materials  at  the^  University  of  Minnesota 
in  a  cooperative  research  program  with  the  Society. 

The  values  given  in  Table  1  show  the  results  of  this  study  and  apply  to 
air  spaces  bounded  by  such  materials  as  paper,  wood,  plaster,  etc., 
having  emissivity  coefficients  of  from  0.9  to  0.95.  The  conductivity 
coefficients  decrease  with  air  space  width  until  a  width  of  about  %  in.  has 
been  reached,  after  which  the  width  has  but  very  little  effect.  In  these 

TABLE  1.    CONDUCTANCES  OF  AIR  SPACES  a  AT  VARIOUS  MEAN  TEMPERATURES 


MIAN 


COITOUCTANCZS  or  AIR  SPACES  FOR  VARIOUS  WIDTHS  IN  INCHES 


TBMP 
DBG  FAHR 

0.128 

0.250 

0.364 

0.493 

0.713 

1.00 

1.500 

20 

2.300 

1.370 

1.180 

1.100 

1.040 

1.030 

1.022 

30 

2.385 

1.425 

1.234 

1.148 

1.080 

1.070 

1.065 

40 

2.470 

1.480 

1.288 

1.193 

1.125 

1.112 

1.105 

50 

2.560 

1.535 

1.340 

1.242 

1.168 

1.152 

1.149 

60 

2.650 

1.590 

1.390 

1.295 

1.210 

1.195 

1.188 

70 

2.730 

1.648 

1.440 

1.340 

1.250 

1.240 

1.228 

80 

2.819 

1.702 

1.492 

1.390 

1.295 

1.280 

1.270 

90 

2.908 

1.757 

1.547 

1.433 

1.340 

1.320 

1.310 

100 

2.990 

1.813 

1.600 

1.486 

1.380 

1.362 

1.350 

110 

3.078 

1.870 

1.650 

1.534 

1.425 

1.402 

1.392 

120 

3.167 

1.928 

1.700 

1.580 

1.467 

1.445 

1.435 

130 

3.250 

1.980 

1.750 

1.630 

1.510 

1.485 

1.475 

140 

3.340 

2.035 

1.800 

1.680 

1.550 

1.530 

1.519 

150 

3.425 

2.090 

1.852 

1.728 

1.592 

1.569 

1.559 

^Thermal  Resistance  of  Air  Spaces  by  F.  B.  Rowley  and  A.  B.  Algren  (A.S.H.V.E.  TRANSACTIONS, 
Vol.  35, 1929,  p.  165). 

coefficients  radiation  is  a  large  factor,  and  if  surfaces  with  low  emissivity 
coefficients  are  substituted  for  ordinary  building  materials  the  total 
amount  of  radiant  heat  will  be  reduced.  The  reduction  in  radiant  heat 
caused  by  the  low  emissivity  surface  is  independent  of  width  of  air  space. 
Air  spaces  properly  formed  in  combination  with  metallic  surfaces  such  as 
aluminum  foil,  coated  sheet  steel,  and  other  materials  having  a  reflective 
surface,  possess  heat  repelling  characteristics.  Values  of  air  spaces 
lined  with  aluminum  foil  on  one  or  both  sides  for  widths  of  %  in.  and  %  in. 
are  shown  in  Table  2  of  conductivities.  A  low  emissivity  coefficient  is 
dependent  on  the  permanency  of  the  reflective  surface.  If  a  bright  clean 
surface  is  covered  with  a  thin  layer  of  corrosive  material  its  reflectivity  is 
appreciably  reduced2. 

In  comparing  the  conductance  coefficients  for  air  spaces  with  and  with- 
out bright  metallic  surface  lining  it  should  be  noted  that  the  reduction  in 
heat  transfer  is  substantially  as  great  when  one  surface  is  lined  as  it  is 
when  both  surfaces  are  lined.  The  reason  for  this  is  that  practically 
95  per  cent  of  the  total  radiant  heat  is  intercepted  by  one  surface  lining 


^Aluminum  Foil  Insulation  (National  Bureau  of  Standards  Letter  Circular  No.  LC465.  June,  1936). 

94 


CHAPTER  5.   HEAT  TRANSMISSION  COEFFICIENTS  AND  TABLES 

and  there  is  but  a  small  amount  left  to  be  stopped  by  the  second  surface 
lining.  The  effect  of  any  low  emissivity  surface  in 'stopping  the  trans- 
mission of  radiant  heat  is  the  same  regardless  of  whether  it  is  on  the  high 
or  low  temperature  side  of  the  air  space.  For  materials  such  as  aluminum 
paint  or  bronze  paint  which  stop  only  a  small  percentage  of  radiant  heat 
there  is  a  greater  percentage  of  gain  by  addition  of  a  second  surface  lining. 

PRACTICAL  COEFFICIENTS 

For  practical  purposes  it  is  necessary  to  have  average  coefficients  that 
may  be  applied  to  various  materials  and  types  of  construction  without 
the  necessity  of  making  tests  on  the  individual  material  or  combination  of 
materials.  In  Table  2  coefficients  are  given  for  a  group  of  materials  which 
have  been  selected  from  various  sources.  Wherever  possible  the  proper- 
ties of  material  and  conditions  of  tests  are  given.  However,  in  selecting 
and  applying  these  values  to  any  construction  a  reasonable  amount  of 
caution  is  necessary;  variations  will  be  found  in  the  coefficients  for  the 
same  materials,  which  may  be  partly  due  to  different  test  methods  used, 
but  which  are  largely  due  to  variations  in  materials.  The  recommended 
coefficients  which  have  been  used  for  the  calculation  of  over-all  coefficients 
as  given  in  Tables  3  to  12  are  marked  by  an  asterisk. 

It  should  be  recognized  in  these  tables  of  calculated  coefficients  that 
space  limitations  will  not  permit  the  inclusion  of  all  the  combinations  of 
materials  that  are  used  in  building  construction  and  the  varied  applications 
of  insulating  materials  to  these  constructions.  Typical  examples  are  given 
of  combinations  frequently  used,  but  any  special  construction  not  given  in 
Tables  3  to  12  can  generally  be  computed  by  using  the  conductivity  values 
given  in  Table  2  and  the  fundamental  heat  transfer  formulae.  For 
example,  the  tabulation  of  all  of  the  values  for  multiple  layers  of  insulating 
materials  would  present  extensive  and  detailed  problems  of  calculations 
for  the  varied  application  combinations,  but  the  engineer  having  the 
fundamental  conductivity  values  can  quickly  obtain  the  proper  coefficients. 

Attention  is  called  to  the  fact  that  the  conductivity  values  per  inch  of 
thickness  do  not  afford  a  true  basis  for  comparison  between  insulating 
materials  as  applied,  although  they  are  frequently  used  for  that  purpose. 
The  value  of  an  insulating  material  is  measured  in  terms  of  its  heat 
resistance,  which  not  only  depends  upon  the  thermal  conductivity  coef- 
ficient per  inch  but  also  upon  the  thickness  as  installed  and  the  manner,  of 
installation.  For  instance  the  material  having  a  coefficient  of  0.50  and 
1  in.  thick  is  equal  in  value  to  a  material  having  a  coefficient  of  0.25  and 
a  thickness  of  J^  in.  Certain  types  of  blanket  installations  are  designed 
to  be  installed  between  the  studs  of  a  frame  building  in  such  manner  as  to 
give  two  air  spaces.  In  order  to  get  the  full  value  of  such  materials  they 
should  be  so  installed  that  each  air  space  is  approximately  1  in.  or  more 
in  thickness  and  the  air  spaces  should  be  sealed  at  the  top  and  bottom  to 
prevent  the  circulation  of  air  from  one  space  to  the  other.  Another 
common  error  in  installing  such  a  material  is  to  nail  the  blanket  on  the 
outside  of  the  studs  underneath  the  sheathing,  in  which  case  one  air 
space  is  lost  and  also  the  thickness  of  the  insulating  material  is  materially 
reduced  at  the  studs.  There  are  certain  other  types  of  insulation  which 
are  very  porous,  allowing  air  circulation  within  the  material  if  not 

95 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 

properly  installed.  The  architect  or  engineer  must  carefully  evaluate  the 
economic  considerations  involved  in  the  selection  of  an  insulating  material 
as  adapted  to  various  building  constructions.  Lack  of  good  judgment  in 
the  intelligent  choice  of  an  insulating  material,  or  its  improper  installation, 
frequently  represents  the  difference  between  good  or  unsatisfactory 
results.  Refer  to  Chapter  7  for  a  discussion  of  wall  condensation. 

Computed  Transmission  Coefficients 

Computed  heat  transmission  coefficients  of  many  common  types  of 
building  construction  are  given  in  Tables  3  to  13,  inclusive,  each  con- 
struction being  identified  by  a  serial  number.  For  example,  the  coefficient 
of  transmission  (IT)  of  an  8-in.  brick  wall  and  J^  in.  of  plaster  is  0.46,  and 
the  number  assigned  to  a  wall  of  this  construction  is  1-B,  Table  3. 

Example  L  Calculate  the  coefficient  of  transmission  (IT)  of  an  8-in.  brick  wall  with 
J£  in.  of  plaster  applied  directly  to  the  interior  surface,  based  on  an  outside  wind  exposure 
of  15  mph.  It  is  assumed  that  the  outside  course  is  of  hard  (high  density)  brick  having  a 
conductivity  of  9.20,  and  that  the  inside  course  is  of  common  (low  density)  brick  having 
a  conductivity  of  5.0,  the  thicknesses  each  being  4  in.  The  conductivity  of  the  plaster  is 
assumed  to  be  3.3,  and  the  inside  and  outside  surface  coefficients  are  assumed  to  average 
1.65  and  6.00,  respectively,  for  still  air  and  a  15  mph  wind  velocity. 

Solution,  k  (hard  high  density  brick)  -  9.20;  x  =  40  in.;  k  (common  low  density 
brick)  =  5.0;  x  «  4.0  in.;  k  (plaster)  =  3.3;  *  =  M  in.;/i  =  1.65;/0  -  6.0.  Therefore, 


6.0  T  9.20  ^  5.0  ~*~  3.3  "*"  1.65 

^  1 

0.167  +  0.435  -i-  0.80  +  0.152  +  0.606 

«  0.46  Btu  per  hour  per  square  foot  per  degree  Fahrenheit  difference  in  tempera- 
ture between  the  air  on  the  two  sides. 

The  coefficients  in  the  tables  were  determined  by  calculations  similar 
to  those  shown  in  Example  1,  using  Fundamental  Formulae  3,  4  and  5 
and  the  values  of  k  (or  C),/i, /0  and  a  indicated  in  Table  2  by  asterisks. 
In  computing  heat  transmission  coefficients  of  floors  laid  directly  on  the 
ground  (Table  10),  only  one  surface  coefficient  (/i)  is  used.  For  example, 
the  value  of  U  for  a  1-in.  yellow  pine  floor  (actual  thickness,  25/32  in.) 
placed  directly  on  6-in.  concrete  on  the  ground,  is  determined  as  follows : 

1 
U  =  ~~; :rir: —  =  0.48  Btu  per  hour  per  square  foot  per  degree  difference 

I         ,    U.  fol     ,       O.U 

1.65    •"  0.80        12.62 
in  temperature  between  the  ground  and  the  air  immediately  above  the  floor. 

Rigid  insulation  refers  to  the  so-called  board  form  which  may  be  used 
structurally,  such  as  for  sheathing.  Flexible  insulation  refers  to  the 
blankets,  quilts  or  semi-rigid  types  of  insulation. 

Actual  thicknesses  of  lumber  are  used  in  the  computations  rather  than 
nominal  thicknesses.  The  computations  for  wood  shingle  roofs  applied 
over  wood  stripping  are  based  on  1  by  4  in.  wood  strips,  spaced  2  in.  apart. 
Since  no  reliable  figures  are  available  concerning  the  conductivity  of 
Spanish  and  French  clay  roofing  tile,  of  which  there  are  many  varieties, 
the  figures  for  such  types  of  roofs  were  taken  the  same  as  for  slate  roofs,  as 


CHAPTER  5.   HEAT  TRANSMISSION  COEFFICIENTS  AND  TABLES 


TABLE  2.    CONDUCTIVITIES  (k)  AND  CONDUCTANCES  (C)  OF  BUILDING 
MATERIALS  AND  INSULATORS** 

The  coefficients  are  expressed  in  Btu  per  hour  per  square  foot  per  degree  Fahrenheit  per  1  in.  thickness, 
unless  otherwise  indicated. 


Material 

Description 

DENSITY 
(La  PER  Cu  FT) 

MEAN  TEMP. 
(DKG  FAHR) 

CoNDDcrivrrr  (K) 

OR 

CONDUCTANCE  (C') 

~l-«  _,jo 

>•           8 

5    3 

| 
<J 

Cement 

Fine 
Aggre- 

0-No.  4 

Coarse 
*gj"   Slump 
No.4-H 

Per 
Cent 
Voids 

SAND  AND  GRAVEL, 

CONCRETE—  

1 
1 

2.00 
2.75 
3.50 
2.00 
2.00 
2.75 
2.75 
3.50 
3.50 

2.75 
4.50 
5.50 
2.75 
2.75 
4.50 
4.50 
5.50 
5.50 

0 

8 

1 

11.5 
10.9 
11.2 
13,9 
13.9 
14.6 
14.6 
14.7 
14.7 

144.7 
145.7 
144.5 
142.5 
142.5 
141.1 
141.1 
139.2 
139.2 

142.3 

75.06 
74.77 
75.00 
75.50 
74.74 
73.30 
74.89 
74.50 
75.15 

13.10 
12.90 
13.20 
12.10 
12.40 
12.40 
12.10 
12.85 
12.50 

12.62* 

0.08 
0.08 
0.08 
0.08 
0.08 
0.08 
0.08 
0.08 
0.08 

1 

4) 
4) 
4) 

4) 
4) 

4) 
4) 
4) 

t! 

(4) 

Avg.  Value  for  Sand  and  Gravel  Concrete  

LlMBSTONE   CONCBETB  

1 
1 
1 
1 

1 
1 

2.00 
2.75 
3.50 
2.00 
2.75 
3.50 

2.75 
4.50 
5.50 
2.75 
4.50 
5.50 

0 
0 
0 
3 

3 

16.6 
15.4 
16.3 
20.9 
23.4 
23.4 

135.3 
137.8 
136.4 
130.1 
126.0 
127.3 

132.15 

74.87 
75.18 
74.75 
74.85 
74.45 
75.26 

11.20 
12.00 
11.50 
10.50 
10.00 
9.79 

10.83 

1   0.09 
0.08 
0.09 
0.10 
0.10 
0.10 

Avg.  Value  for  Limestone  Co 

ncfftte 

CINDBR  CONCRETE  

1 
1 
1 

1 
1 

1 

2.00 
2.75 
3.50 
2.00 
2.75 
3.50 

2.75 
4.50 
5.50 
2.75 
4.50 
5.50 

0 
0 
0 
3 
3 
3 

18.2 
19.9 
21.4 
22.8 
26.0 
24.4 

103.6 
98.7 
92.0 
101.4 
94.0 
94.4 

97.35 

75.26 
75.71 
75.72 
74.95 
75.20 
75.55 

4.63 
4.30 
3.73 
4.89 
4.38 
4.24 

4.86 

0.22 
0.23 
0.27 
0.20 
0.23 
0.24 

4) 

I 

4) 
4) 

Avg.  Value  for  Cinder  Concrt 

>te 

HATDITE  ,„. 

1 
1 
1 
1 
1 
1 
1 

2.00 
2.75 
3.50 
2.00 
2.75 
2.75 
3.50 

2.75 
4.50 
5.50 
2.75 
4.50 
4.50 
5.50 

0 
0 
0 

4 
4 
4 
4 

18.0 
19.8 
21.8 
21.2 
22.2 
22.2 
23.9 

80.7 
75,0 
71.7 
78,8 
72.4 
72.4 
71.0 

74.57 

74.82 
75.75 
74.82 
74.76 
75.39 
75.49 
75.46 

4.15 
3.78 
3.67 
4.38 
3.89 
3.86 
4.00 

3.96 

0.25 
0.26 
0.27 
0.23 
0.26 
0.26 
0.25 

4) 
4) 

3 
3 

4) 

Avg.  Value  f  or  Haydite  , 

AUTHORITIES: 

JU.  S.  Bureau  of  Standards,  tests  based  on  samples  submitted  by  manufacturers. 

'A.  C.  Willard,  L.  C.  Lichty,  and  L.  A.  Harding,  tests  conducted  at  the  University  of  Illinois. 

*J.  C.  Peebles,  tests  conducted  at  Armour  Institute  of  Technology,  based  on  samples  submitted  by 
manufacturers. 

*F.  B.  Rowley,  tests  conducted  at  the  University  of  Minnesota. 

5A.S.H.V.E.  Research  Laboratory. 

•E.  A.  Allcut,  tests  conducted  at  the  University  of  Toronto. 

'Lees  and  Charlton. 

8G.  B.  Wilkes,  tests  conducted  at  the  Massachusetts  Institute  of  Technology. 

*Recommended  conductivities  and  conductances  for  computing  heat  transmission  coefficients. 

tFor  thickness  stated  or  used  on  construction,  not  per  1-in.  thickness. 

«For  additional  conductivity  data  see  Chapters  3  and  15, 1937  A.S.R.E.  Data  Book. 

klf  outside  surface  of  block  is  painted  with  an  impervious  coat  of  paint,  add  0.07  to  resistance  for  sand 
and  gravel  blocks.  Add  0.18  to  resistance  for  cinder  blocks.  Add  0.17  to  resistance  for  haydite  blocks. 

"Recommended  value.  See  Heating,  Ventilating  and  Air  Conditioning,  by  Harding  and  Willard,  revised 
edition,  1932. 

dSee  A.S.H.V.E.  Research  Paper,  Conductivity  of  Concrete,  by  F.  C.  Houghten  and  Carl  Gutberlet 
(A.S.H.V.E.  TRANSACTIONS,  Vol.  38,  1932,  p.  47). 

<The  6-in.,  8-in.t  and  10-in.  hollow  tile  figures  are  based  on  two  cells  in  the  direction  of  heat  now.  The 
12-in.  hollow  tile  is  based  on  three  cells  in  the  direction  of  heat  flow.  The  16-in.  hollow  tile  consists  of  one 
10-in.  and  one  6-in.  tile,  each  having  two  cells  in  the  direction  of  heat  flow. 

"Roofing,  0.15-in.*  thick  (1.34  Ib  per  SQ  ft),  covered  with  gravel  (0.83  Ib  per  sq  ft),  combined  thickness 
assumed  0.25. 

•  ASurface  values  were  obtained  on  vertical  surfaces  and  varying  with  the  temperature  differences.  A 
foil  lined  air  space  in  a  horizontal  position  will  have  a  coefficient  roughly  three  times  greater  if  the  heat 
flow  is  upward  rather  than  downward. 

97 


HEATING  VENTILATING  AIR  CONDITIONING  GUIDE  1938 


TABLE  2.    CONDUCTIVITIES  \k)  AND  CONDUCTANCES  (C)  OF  BUILDING 
MATERIALS  AND  INSULATORS— Continued 

The  coeficients  are  expressed  in  Biu  per  hour  per  square  foot  per  degree  Fahrenheit  per  1  in.  thickness 
unless  otherwise  indicated. 


Material 

Description 

DENSITY 
(LB  PER  Cu  FT) 

IMEAN  TEMP. 
(DEQ  FAHR) 

CONDUCTIVITY  (fc) 

OR 

CONDUCTANCE  (C) 

g  g 

hi 

EH 
1 

Fine      Coarse                  per 
•  O-No.  4   No.  4-J^           ,      01 

EXPANDED  BUBNED  CLAY  1       ,    8.00                               18.4 
STBAJC  TREATED  LIMESTONE  SLAG-  j     1       ;    7.00                              27.1 
PUIIICI;  MTNED  TN  CAT.TF  1        ;    8.00                               26.5 

57.9 
74.6 
65.0 

75.57 
74.49 
74.68 

2.28 
2.27 
2.42 

0.44 
0.44 
0.41 

(4) 
(4) 
(4) 

BY-PHODUCT  OF  MANUFACTURE     '      1       ,8.00         Modulus          25.5 
OF  PHOSPHATES  '     1       1    8.00            3.75             21.1 

86.6 
91.1 

74.62 
74.43 

3.19 
3.42 

0.31 
0.29 

(4) 
(4) 

HATDIT 

1        j    8.50                                21.8 
1        i    8.50                                 21.8 

67.1 
67.1 

75.89 
74.60 

2.89 
2.815 

0.35 
0.34 

(4) 
(4) 

f  •  l  «  16  l-w*  CM  cwwTfft  ttocn 

Sand  and      v  1            te 

126.4 

40 

40"~ 
40 
40 

40"' 

40 
40 
40 
40 

0.900 

1.000 
0.560 
0.856 
0.577 
0.600 
0.390 
0.250 
0.266 
0.495 
0.206 

\ 

F 

•* 

,* 

* 
* 
* 

l.ll 

1.00 
1.79 
1.17 
1.73 
1.66 
2.56 
4.00 
3.76 
2.02 
4.85 

(4) 

2 

4) 

ti 

4) 

t! 
i! 

Sand  and  gravel  aggregate  used  for  calcu- 
lations          _  

a-  ]• 

^j  ^JL* 

At 

Cores  filled  with  5.  14  Ib  density  cork  
Crushed  limestone  aggregate 

134.3 
86.2 

Cinder  aggregate   ,_  ,  

Cinder  aggregate  used  for  calculations—  ~ 

Cores  filled  with  69.7  Ib  density  cinders  
Cores  filled  with  5  .  12  Ib  density  cork- 

J5J-  

Cores  filled  with  U.2  Ib  density  rock  wool  
TIftydite  aggregate 

67.7 

Cores  MeJTwith  5.06  Ib  density  cork  

8>12 

,,63.c*~«  <*«**> 

*«>', 

Sand  and  gravel  aggregate..™  „_  
Sand  and  gravel  aggregate  used  for  calcu- 
lations             i                        ,  .  -  „ 

124.9 

40 

0.777f 

O.SOOf* 
0.531f* 
0.237f* 
0.468f 
0.168f* 

1.29 

1,88 
4.22 
2.13 
5.94 

(4) 
4) 

tl 

4) 
4) 

->} 

L 

Or 
1 
x_S*-  ' 

If 

T, 

Cinder  aggregate—  ~—~-.—.-~..~—  _...__.. 
Cores  filled  with  5.24  Ib  density  cork.  

86.2 
__, 

40 
40 
40 
40 

Cores  filledwith  5  .6  Ib  density  cork.  

.5f                        -f 

-.jvrf 

Cinder  aggregate-  

Double  waU  with  1  in.  air  space  between  
1  in.  space  filled  with  9.97  ID  density  rock  wool 

100.0 
100.0 
100.0 

40 
40 
40 

l.OOOf 
0.358f 
0.204f 

1.00 
2.70 
4.90 

4) 
4) 
4) 

(4) 

!> 

—  j  run  r~ 

=  >  i 

,           .s,           , 

,.n  *_ 

5x8x12  block  sand  and  gravel  aggregate™. 

133.7 

40 

0.380f 

2.6.? 

JJ'^^E 

gtjij 

iin^1^ 

-rH* 

1 

-,*-•*-,  -" 

5x8x12  block  sand  and  gravel  aggregate*.. 

134.0 

40 

0.947f 

1.06 

(4) 

Ti! 

ilT 

m 

u» 

For  notes  see  Page  97. 


CHAPTER  5.    HEAT  TRANSMISSION  COEFFICIENTS  AND  TABLES 


TABLE  2. 


CONDUCTIVITIES  (k)  AND  CONDUCTANCES  (C)  OF  BUILDING 
MATERIALS  AND  INSULATORS — Continued 


The  coefficients  are  expressed  in  Btu  per  hour  per  square  jopt  per  degree  Fahrenheit  per  1  in.  thickness, 
unless  otherwise  indicated. 


Material 

Description 

DENSITY 
(LB  PER  Cu  FT) 

II 
li 

CONDUCTIVITY  (Jt) 

OR 

CONDUCTANCE  (C') 

-M'rf*     -T'O 

T.T 

3    « 

t« 

-aj 

MASONRY  MATERIALS 

Low  density  

5.00* 
9.20* 
5.00* 
12.00* 
ll.SSfo1 
16.36 
1.06 
1.44 
1.80 
2.18 

1.66* 

3.98 
12.50* 
12.00* 

i.oot* 

0.64f* 
0.60f* 
0.58f* 
0.40f* 
0.31t* 

i.oot 

0.60t 
0.47t 
0.46t* 
1.66 
2.96 
12.00* 

0.20 
0.11 
0.20 
0.08 

0.94 
0.69 
0.56 
0.46 

0.60 

0.25 
0.08 
0.08 
1.00 
1.57 
1.67 
1.72 
2.50 
3.23 
1.00 
1.67 
2.13 
2.18 
0.60 
0.34 
0.08 

(5 

1 

(3) 
(3) 
(3) 

(4) 
(3) 

High  density 

75 
75 
75 
75 

74 
70 

Damp  or  wet 

CEMENT  MORTAR.  —  
CONCRETE  

STONE  

SrrjCCO  _  _ 

TILE. 

Typical                       .             .  -   —  

40.0 
50.0 
60.0 
70.0 

51.2 
101.0 

Various  ages  and  mixes''  .  
Cellular 

Cellular_  
Cellular                                      ..     

Cellular  

Typical  fiber  gypsum,  87.5%  gypsum  and 
12.5%  wood  chips  
Special  concrete  made  with  an  aggregate  of 
hardened  clay~—l-2~3  mix_-,..~  
Typical-              .  

Typical        ..  



Typical  hollow  clay  4  in.) 

TILE  OR  TBHRAZZO  

Typical  hollow  clay  6  in.)*  





Typical  hollow  clay  8  in.)*  _      -     ..-  — 

Typical  hollow  clay  10  in.)"  - 

Typical  hollow  clay  12  in,)*  
Typical  hollow  clay  16  in,)*  —     



no" 

100 

105 

"70" 

76 

(2) 

8 
@ 

Hollow  clay  (2  in.)H-in.  plaster  both  sides  — 
Hollow  clay  (4  in.)  J^-in.  plaster  both  sides  — 
Hollow  clay  (6  in.)  l/fcaa.  plaster  both  sides.  — 
Hollow  gypsum  (4  in.)  _  
Solid  gypsum  _  
Solid  gypsuin_—..-  -  — 
Typical  flooring-  

120.0 
127.0 
124.3 

YlT 
75.6 

INSULATION—  BLANKET 
OR  FLEXIBLE  TYPES 

FlBlR- 

Typical  

3.62 
4.60 
3.40 
4.90 

5.76 

7.70 
11.00 
1.00 
6.70 

12.1 

70 
90 
90 
90 

71 

71 
75 
90 
75 

75 

0.27* 

0.25 
0.26 
0.25 
0.28 

0.26 

0.28 
0.25 
0.24 
0.25 

0.40t 

3.70 

4.00 
3.85 
4.00 
3.57 

3.85 

3.57 
4.00 
4.17 
4.00 

2.50 

(3) 
1) 
1) 
(1) 

(3) 
(3) 

@ 

(3) 
(4) 

Chemically  treated  wood  fibers  held  between 
layers  of  strong  pjiper/.,..  _  -.„-     -  - 

Eel  grass  between  strong  paper/  

Flax  fibers  between  strong  paper/.  
Chemically  treated  hog  hair  between  kraf  t 
paper/                             —     

Chemically  treated  hog  hair  between  kraft 
paper  and  asbestos  pap?!1/  „       -  - 

Hair  felt  between  layers  "of  paper/       

Kapok  between  burlap  or  paper/  
Jute  fiber/                 ...        .  

Ground  paper  between  two  layers,  each  %-in. 
thick  maae  up  of  two  layers  of  kraft  paper 
(sample  %-in.  thick)  — 

INSULATION—  SEMI- 
RIGID  TYPE 

FlBBR  

Felted  cattle  h^>/ 

13.00 
11.00 
12.10 
13.60 
7.80 
6.30 
6.10 
6.70 
10.00 
11.00 

90 
90 
70 
90 
90 
90 
90 
75 
90 
70 

0.26 
0.26 
0.30 
0.32 
0.28 
0.27 
0.26 
0.25 
0.37 
0.26 

3.84 
3.84 
3.33 
3.12 
3.57 
3.70 
3.85 
4.00 
2.70 
3.84 

1) 
1) 

1) 

i 

i) 

3) 

K                 UK 

Flax/                          .     —       —       -     - 

Flax  and  rye/  
Felted  hair  and  asbestos/    - 

75%  hair  and  25%  jute/ 

50%  hair  and  50%  jute/          ..  _ 

jute/                   "'       ._  ._           

Felted  jute  and  asbestos/    -       .  

Compressed  peat  moss  

INSULATION—LOOSE 
FILL  OR  BAT  TYPE 
"BY*™* 

Made  from  ceiba  fibers/  

a        «          a            «                       ^  

1.90 
1.60 

75 
75 

0.23 
0.24 

4.35 
4.17 

(3) 
(3) 

For  notes  see  page  97. 


99 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


TABLE  2.    CONDUCTIVITIES  (k)  AND  CONDUCTANCES  (C)  OF  BUILDING 
MATERIALS  AND  INSULATORS — Continued 

The  efficients  are  expressed  in  Btu  fer  hour  per  square  foot  per  degree  Fahrenheit  per  1  in.  thickness, 
unless  otherwise  indicated. 


Material 

Description 

DENSITY 
(Ln  PER  Cu  FT) 

MEAN  TEMP. 
(DBG  FAHR) 

CONDUCTIVITY  (fc) 

OR 

CONDUCTANCE  (C) 

~  js  ^|O 

g    Y   E 

|si   1 

S    S    5 

INSLT.ATION  -LOOSE 
FILL  OR  BAT  TYPE 
—Continued 

GLASS  Wool  
GRANULAR. 

Fibrous  material  made  from  dolomite  and 
silica.—                 ....          i        • 

1.50 
9.40 

1.50 
4.20 

6.20 
30.00 
24.00 
18.00 
12.00 
34.00 
26.00 
24.00 
19.80 
18.00 

ITlO 
21.00 
18.00 
14.00 
10.00 
14.50 
14.50 
11.50 
12.00 
8.80 
13.20 
3.00 

75 
103 

75 
72 

42 
90 
90 
90 
90 
90 
90 
75 
90 
75 

90 
90 
90 
90 
90 
77 
75 
72 
90 
90 
90 
90 

0.27 
0.27 

0.27 
0.24 

0.32 
1.00 
0.77 
0.59 
0.44 
0.60 
0.52 
0.48* 
0.35 
0.34 
0.27* 
0.31 
0.30 
0.29 
0.28 
0.27* 
0.33 
0.38 
0.31 
0.41 
0.41 
0.36 
0.31 

3.70        (3) 
3.70        (1) 

3.70        (3) 
4.17         (3) 

3.12          3) 
.00          1) 
.30          1 
.69          1 
.27          1 
.67          1 
.92          1 
2.08          3) 
2.86         1) 
2.94          3) 
3.70         _ 
3.22          1) 
3.33          1 
3.45          1 
3.57          1) 
3.70          1) 
3.03          1) 
2.63          3) 
3.22          3) 
2.44          1 
2.44          1 
2.78          1) 
3.22          1) 

Fibrous  material  made  from  slag  
Fibrous  material  25  to  30  microns  in  dia- 
meter, made  from  virgin  bottle  glass  
Made  from  combined  silicate  of  lime  and 
alumina                                  

MINERAL  WOOL.  

RlORANULATZD  COBK  

ROCK  WOOL 

Made  from  expanded  aluminum-magnesium 
silicate 

Cellular  dry 

«         u 

ti            a. 

Flaked  dry  and  fluffy-' 
pjasea,  ary  ana  nuny  

a          u       u          u 

u          u       u          u 

u          u       *          u 

All  forms  typical                  t  

About  3to-in  particles         

Fibrous  material  made  from  rock  .  

SAWDUST^.,  ^  t  _,  T 

It                        U                  U               U               U 

ff                 u            ft          u          a 

tt                        It                  U               «               It 

Rock  wool  with  a  binding  agent  
Rock  wool  with  flax,  straw  pulp,  and  binder 
Rock  wool  with  vegetable  fibers 

Various  ,  

SHAVTWGS 

Various  from  planer 

From  maple,  beech  and  birch  (coarse)  
Redwood  bark 

INSULATION—  RIGID 
FEBBB  „„ 

Typical                          

14760 
10.60 
7.00 
5.40 
14.50 

10.00 
15.00 
17.90 
15.20 

54.00 
16.10 
19.30 
24.20 
13.50 

13.80 
17.00 
15.90 
15.00 

90 
90 
90 
90 
90 

75 
71 
78 
70 

75 
81 
86 
72 
70 

70 
68 
72 
70 
52 
72 

0.30* 
0.34 
0.30 
0.27 
0.25 
0.32 
0.33* 

0.28 
0.33 
0.36 
0.32 

1.07f 
0.34 
0.51 
0.46 
0.33 

0.30 
0.33 
0.33 
0.33 
0.33 
0.29 
0.33 
0.34 

3.33         - 
2.94        (1) 
3.33         (1) 
3.70        (1) 
4.00        (1) 
3.12         (1) 
3.03         ._ 

3.57          3) 
3.03          3) 
3.12          4) 
3.12          3) 

0.93          3) 
2.94          3 
1.96          1 
2.17          3) 
3.03          3) 

3.33          3 
3.03          3 
3.03          3 
3.03          3) 
3.03          6) 
3.45          3) 
3.03          3) 
2.94        (1) 

No  added  binder  

tt       a            u 

UK             u 

it        it             it 

Asphaltic  binder  .._.   ._. 

Typical                                               

Chemically  treated  hog  hair  covered  with 
film  of  asphalt 

Madfl  from  1*1171  staHn? 

•     "    exploded  wood  fibers  
•     tt    hard  wood  fibers  
Insulating  plaster  9/10-in.  thick  applied  to 
£|-in.  plaster  board  base 

M?M?e  from  licorice  roots 

Made  from  85%  magnesia  and  15%  asbestos 
Made  from  shredded  wood  and  cement  
"     a    sjigar  nans  fiber,  JL  . 

Sugar  cane  fiber  insulation  blocks  encased  in 
asphalt  membrane 

Made  from  wheat  straw             --,,-,-,, 

«             wnnd  fiber 

« 

B 

* 

8.50 
15.20 
16.90 

« 

u 

90 

BUILDING  BOARDS 
\SR-Kfrrnx 

123.00 
20.40 

86 
110 

2.70 

0.48 

0.37         (1) 
2.08        (2) 

Corrugated  asbestos  board  

For  notes  see  Pa^e  97. 


100 


CHAPTER  5.    HEAT  TRANSMISSION  COEFFICIENTS  AND  TABLES 


TABLE  2.    CONDUCTIVITIES  (k)  AND  CONDUCTANCES  (C)  OF  BUILDING 
MATERIALS  AND  INSULATORS— Continued 

The  coefficients  are  expressed  in  Btu  per  hour  per  square  foot  per  degree  Fahrenheit  per  1  in.  thickness 
unless  otherwise  indicated. 


Material 

Description 

DENSITY 
(La  PER  Cu  FT) 

MBAN  TBMP. 
(DEQ  FAHR) 

CONDUCTIVITY  (fc) 

OR 
CONDUCTANCE  (C) 

~  \**  ~  !cj 

i    i 

«! 

BUILDING  BOARDS 
—Continued 
ASBESTOS  ~  

Pressed  asbestos  mill  board  _     

Sheet  MhfiRtns  

60.50 
48.30 

86 
110 

0.84 
0.29 

1.19 
3  45 

(1) 

?) 

GYPSUM——  -...—  

Gypsum  between  layers  of  heavy  paper  
Rigid,  gypsum  between  layers  of  heavy 
paper  (H-in.  thick)  

62.80 
53.50 

70 
90 

1.41 
2.60f 

0.71 
0.38 

3) 
(1) 

PLASTER  BOARD.._  _  „. 

Gypsum  muted  with  sawdust  between  layers 
of  heavy  paper  (0.39-in.  thick)  
(*$  in  ) 

60.70 

90 

3.60f 
3.73J* 

0.28 
0.27 

(1) 

(fcin.)  -   



— 

2.82f* 

0.35 

- 

ROOFING  CONSTRUCTION 
ROOTING             .  - 

Asphalt,  composition  or  prepared 

70  00 

75 

6  50t* 

0  15 

0) 

Built  up-—  iNP11  tniftk    *"   *" 

3.53f* 

0.28 

Built  up,  bitumen  and  felt,  gravel  or  slag 
snrfaftftdff      T  T     T 

1.33 

0.75 

(2) 

Plaster  board,  gypsum  fiber  concrete  and 

3-ply  roof  roaring  ?V£  i^   thick 

52  40 

76 

0.58f 

1.72 

4) 

SHTNGT/I&S       —  -^  -. 

AaWWi 

65.00 

75 

6.00f* 

0.17 

3) 

A«trhfl.|t 

70.00 

75 

6.50t* 

0.15 

3) 

RlfttA 

201.00 

10.37* 

0  10 

7) 

Wood  

1.28f* 

0.78 

PLASTERING  MATERIALS 
PLASTER 

foment 

8.00 

0.13 

(?) 

Gyp?UTn  typififtl 

3.30* 

0.30 

Thifi1rr,P*s  3^  in 

73 

8.80t 

0.11 

(4) 

METAL  T,ATW  ^NP  PT.ASTTB^ 

Total  thielcnfisa  %  in. 

4.40t* 

0.23 

WOOD  LATH  AND  PLASTER  

54-in.  plaster,  total  thickness  %  in  



70 

2.  50t* 

0.40 

(4) 

BUILDING 
CONSTRUCTIONS 

FBAMD- 

1-in,  fir  sheathing  and  buiMing  paper 

30 

0.71t* 

1.41 

(4) 

1-in.   fir   sheathing,   building  paper,   and 

20 

O.SOf* 

2.00 

(4) 

1-in.  fir  sheathing,  building  paper  and  stucco 
Pine  lap  siding  and  building  paper-~siding 

4  in   wi^e        ,                          !, 



20 
16 

0.55 
O.SSf* 

1.82 
1.18 

(4) 
(4) 

Yellow  pine  tap  siding.    .--    

1.28t* 

0.78 

FLOORING  ._  - 

Maple  —  across  grain..^_    ..  ,  ^1J..,     

40.00 

75 

1.20 

0.83 

(3) 

Bfttt'fisnip  linoleum  (M-"1  )     "  

1.36f* 

0.74 

AIR  SPACE  AND  SURFACE 
COEFFICIENTS 

Am  ftPAdftH      

Over  %-in.  faced  with  ordinary  building 

materials 

40 

I.IO"* 

0.91 

(4) 

SURFACES,  ORDINARY 

fitill  »ur  (/i) 

1.6St* 

0.61 

(4) 

15  mph  —  (/o)         .  ,«.....  ,  ,- 

6.  00-* 

0.17 

(4) 

SURFACE  ROUGH  STUCCO 

p.oot* 

0.11 

(4) 

SURFACE,  BRIGHT  ALTTMTVTTM 

Still  9)f  (/i)11 

o.sot 

1.25 

(«) 

AIR  SPACES  FACED  WITH 
BRIGHT  ALUMINUM 
FOIL 

Air  space,  faced  one  side  with  bright  alumi- 
num foil  over  M-"1-  win"fc 

50 

0.46f* 

2.17 

(4) 

Air  space,  faced  one  side  with  bright  alumi- 
num foil  iHj-in  wide 

50 

0  62t 

1.61 

(4) 

Air  space,'  faced  both  sides.  with  bright 
aluminum  foil,  over  %-in.  wido   ,  ., 
Air  space,  faced  both  sides  with  bright 
aluminum  foiL  ^-in  wiH^,rT,      T  



50 
50 

0.41f* 
O.S7f 

2.44 
1.75 

(4) 
(4) 

For  notes  see  Page  97. 


101 


HEATING  VENTILATING  AIR  CONDITIONING   GUIDE  1938 


TABLE  2.    CONDUCTIVITIES  (A)  AND  CONDUCTANCES  (C)  OF  BUILDING 
MATERIALS  AND  INSULATORS — Continued 

The  coefficients  are  expressed  in  Btu  per  hour  per  square  foot  per  degree  Fahrenheit  per  1  in.  thickness, 
unless  otherwise  indicated. 


Material 

Description 

DBNBPrr 
(La  PER  Cu  FT) 

LMEAN  TEMP. 
(Duo  FAHR) 

CONDUCTIVITY  (Jk) 

OR 

CONDUCTANCE  (C) 

H*  -<|o 

AIR  SPACES  FACED  WITH 
BRIGHT  ALUMINUM 
FOIL—Continued 

Air  space  divided  in  two  with  single  curtain 
of  bright  aluminum  foil  (both  sides  bright) 
Each  space  over  ?^i"in  wide    

50 

0.23f* 

4.35         (4) 

Each  gp&ce  J^o-in.  wide                 .    .  ,.,.., 

SO 

0.31f 

3.23         (4) 

Air  space  with  multiple  curtains  of  bright 
aluminum  foil   bright  on  both  sides, 
curtains  more  than  %-in.  apart,  ah*  circu- 
lation between  spaces  prevented: 
2  curtains  fonnjpg  3  npfurflfi  

50 

O.lSf* 

6.78         (4) 

3  curtains  forming  4  spaces 

50 

O.llf* 

9.22         (4 

4  curtains  forming  5  spaces             L-.L^,,r 

50 

0.09f* 

11.66        (4 

SPACES  FACED  WITH  NOX- 
METALLIC  REFLECTIVE 
SURFACE 

Fabric  with  non-metallic  reflective  surface 
06  in.  thick)  placed  in  center  of  a  1M  in- 

ftir  spare 

70 

0.33f 

3.03         (4) 

Core  o'f  fiber  board  coated  two  sides  with 
non-metallic   reflective  surface    (%   in. 
thick)  placed  in  space  having  approxi- 
mately %  in.  air  space  on  each  side  
Fiber  board  coated  one  side  with  non- 
metallic  reflective  surface  (%  in.  thick) 
placed  in  space  having  approximately 
*•£  in  air  space  on  each  side 

23.4 

70 
75 

0.27f 
0.49f 

3.70         (3) 
2.04         (3) 

Air  space  divided  in  two  with  fabric  faced 
both  sides  with  non-metallic  reflective 
surface,  each  space  over  %-in.  wide  
Air  space  over  J^-in.  wide  faced  one  side 
with  non-metallic  reflective  surface  



40 
40 

0.33f 
0.67f 

3.03         (4) 
1.49         (4) 

WOODS  (Across  Grain) 
RA.TJU 

20.0 

90 

0.58 

1.72         (1) 

8.8 

90 

0.38 

2.63           ) 

7.3 

90 

0.33 

3.03            ) 

CALIFORNIA.  REDWOOD 

QO7  TnoTfitdire 

22.0 

75 

0.66 

1.53            ) 

QCT 

28.0 

75 

0.70 

1.43            ) 

R°? 

22.0 

75 

0.70 

1.43            ) 

807 

28.0 

75 

0.75 

1.33            ) 

16or 

22.0 

75 

0.74 

1.35            ) 

Ifi^jj 

28.0 

75 

0.80 

1.25          4) 

CYPRXSB 

28.7 

86 

0.67 

1.49          1) 

DoijoffAs  FIR 

0%  moisture  „  .   ,           ...  „  

26.0 

75 

0.61 

1.64          4) 

34.0 

75 

CT.67 

1.49          4) 

R<7 

26.0 

75 

0.66 

1.52          4) 

fl^ 

34.0 

75 

0.75 

1.33          4) 

16%                  .  ,1Lll            „    t  

26.0 

75 

0.76 

1.32          4) 

34.0 

75 

0.82 

1.22          4) 

EAHTWN  Hmnx»Cif 

Cty  Tnniftf.nre 

22.0 

75 

0.60 

1  67          4) 

ftor 

30.0 

75 

0.76 

1.32          4) 

R% 

22.0 

75 

0.63 

1.59          4) 

9P7 

30.0 

75 

0.81 

1.23          4) 

16% 

22.0 

75 

0.67 

1.49        (4) 

30.0 

75 

0.85 

1.18        (4) 

HARD  MAPLJC..         ...  „ 

0*7  mofctrire 

40.0 

75 

1.01 

0.99         (4) 

QOT 

46.0 

75 

1.05 

0  95          4) 

W/ 

40.0 

75 

1.08 

0.93         4) 

s% 

46.0 

75 

1.13 

0.89          4) 

16% 

40.0 

75 

1.15 

0.87          4) 

Ifi% 

46.0 

75 

1.21 

0.83          4) 

For  notes  see  Page  97. 


102 


CHAPTER  5.   HEAT  TRANSMISSION  COEFFICIENTS  AND  T ABIDES 


TABLE  2. 


CONDUCTIVITIES  (k)  AND  CONDUCTANCES  (O  OF  BUILDING 
MATERIALS  AND  INSULATORS — Continued 


The  coefficients  are  expressed  in  Btu  per  hour  per  square  foot  per  degree  Fahrenheit  per  1  in.  thickness, 
unless  otherwise  indicated. 


Material 

Description 

DKNSITT 
(La  pin  Cu  FT) 

MEAN  TEMP. 
(DEQ  FAHR) 

CONDUCTIVITT  (k) 
on 
CONDUCTANCB  (C) 

-'•*  ^'0 

s  & 

j 

WOODS—  Continued 
LONGLIBAF  YELLOW  Pirns 

0%  moisture  __„„,  Tir,  r  

30.0 

7S    ! 

0.76 

1.32 

f4) 

40.0 

75 

0.86 

1.16 

(4) 

R<y 

30.0 

75 

0.83 

1.21 

(4) 

gar 

40.0 

75     ! 

0.95 

1.05 

(4) 

Ifi%                  ril  ...  ,      __.,.,          

30.0 

7S 

0.89 

1.12 

(4) 

16% 

40.0 

75 

1.03 

0.97 

(4) 

MAHQGANT 

34.3 

86 

0.90 

1.11 

(1) 

MjLPT.TH 

44.3 

86 

1.10 

0.91 

(1) 

\IAPLIB  OB  OAK_ 

1.15* 

0.87 

NORWAY  PINE 

0%  moisture   - 

22.0 

75 

0.62 

1.61 

(4) 

32.0 

75 

0.74 

1.35 

4) 

oCff 

22.0 

75 

0.68 

1.47 

4) 

ty? 

32.0 

75 

0.83 

1.21 

4) 

16%                                                                                     ,,         L 

22.0 

75 

0.74 

1.35 

4) 

16% 

32.0 

75 

0.91 

1.10 

4) 

TJ         CfWXBS 

0%  moisture  ...  L 

22.0 

75 

0.67 

1.49 

4) 

32.0 

75 

0.79 

1.27 

4) 

ow 

22.0 

75 

0.71 

1.41 

4) 

gar 

32.0 

75 

0.84 

1.19 

4) 

169r 

22.0 

75 

0.74 

1.35 

4) 

16% 

32.0 

75 

0.90 

1.11 

4) 

RED  OAK 

0%  m^i"?  ure 

38.0 

75 

0.98 

1.02 

4) 

48.0 

75 

1.18 

0.85 

4) 

oar 

38.0 

75 

1.03 

0.97 

4) 

oft? 

48.0 

75 

1.24 

0,81 

4) 

16% 

38.0 

75 

1.07 

0.94 

4) 

16% 

48,0 

75 

1.29 

0.78 

4) 

SHQBTLHAi1  YBLLOW  PINTS 

26.0 

75 

0.74 

1.35 

4) 

36.0 

75 

0.91 

1.10 

4) 

oar 

26.0 

75 

0.79 

1.27 

4) 

Offi? 

36.0 

75 

0.97 

1.03 

4) 

16?^ 

26.0 

75 

0.84 

1.19 

4^ 

16% 

36.0 

75 

1.04 

0.96 

4) 

BofT  KLM 

28.0 

75 

0.73 

1.37 

4) 

QOT 

34.0 

75 

0.88 

1.14 

L) 

gar 

28.0 

75 

0.77 

1.30 

4) 

8y 

34.0 

75 

0.93 

1.08 

4) 

169^ 

28.0 

75 

0,81 

1.24 

4 

jgar 

34.0 

75 

0.97 

1.03 

t 

SOFT  MAPLE- 

0^  moisture 

36.0 

75 

0.89 

1.12 

4) 

09* 

42.0 

75 

0.95 

1.05 

4) 

8?^ 

36.0 

75 

0.96 

1.04 

4) 

007 

42.0 

75 

1.02 

0.98 

4) 

16^ 

36.0 

75 

1.01 

0.99 

4) 

16*7 

42.0 

75 

1.09 

0.92 

4 

SUGAR  PTNIE 

0%  moiB  ure            ...L.,^  ,„  .r 

22.0 

75 

0.54 

1.85 

4 

28.0 

75 

0.64 

1.56 

4 

8v 

22.0 

75 

0.59 

1.70 

4} 

oof 

28.0 

75 

0.71 

1.41 

4} 

169^ 

22.0 

75 

0.65 

1.54 

4) 

167 

28.0 

75 

0.78 

1.28 

4) 

VIRGINIA.  PINB 

0 

34.3 

86 

0.96 

1.04 

1) 

WEST  COAST  BJBMLOCK. 

0%  moisture                         -..r. 

22.0 

75 

0.68 

1.47 

4) 

30.0 

75 

0.79 

1.27 

4) 

Ott? 

22.0 

75 

0.73 

1.37 

4} 

am 

30.0 

75 

0.85 

1.18 

4) 

16v 

22.0 

75 

0.78 

1.28 

4) 

jg07 

30.0 

75 

0.91 

1.10 

4) 

WH    «  p___ 

31.2 

86 

0.78 

1.28 

1) 

YELLOW  PTKB 

1.00 

1.00 

3) 

0.80* 

1.25 



For  notes  see  Page  97. 


103 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


TABLE  3.   COEFFICIENTS  OF  TRANSMISSION  (U)  OF  MASONRY  WALLS* 

Coefficients  are  expressed  in  Blu  per  hour  per  square  foot  per  degree 
Fahrenheit  difference  in  temperature  between  the  air  on  the  two  sides, 
and  are  based  on  a  wind  Telocity  of  15  mph. 


} 

THICKNESS 

T 

YP 

ICAL 

OF 

WALL 

CONSTRUCTION                                       TYPE  OF  WALL 

MASONRY 

No. 

(INCHES) 

r< 
=3*5 

aa= 

a 

3t 

P* 

i 

=S^ 

3 

*>H 

^> 

& 

Solid  Brick 

Based  on  4-in.  hard  brick  and  the  remainder 

8 
12 

1 
2 

^a 
te*= 

•*** 

=2** 

£ 

s 

•**. 

^2 
3? 

t 

common  brick. 

16 

3 

t 

•3^ 

g 

./TU&C( 
«ss*^±±S 

)N 

Hollow  Tile 

Stucco  Exterior  Finish. 
The  8-in.  and  10-in.  tile  figures  are  based  on 

8 

4 

1 

^5 

!S7 

B 

two  cells  in  the  direction  of  flow  of  heat.  The 

10 

Q 

12-in.  tile  is  based  on  three  cells  in  the  direc- 

12 

6 

y 

g 

tion  of  flow  of  heat.    The  16-in.  tile  consists 

16 

7 

1 

I 

1 

r 

^ 

of  one  10-in.  tile  and  one  6-in.  tile  each  having 

*4K 

UL 

•», 

**^ 

r 

r 

two  cells  in  the  direction  of  heat  flow. 

c 

t 

C! 

—  "^ 

5 

9 

8 

8 

N. 

Jar: 

—  %<? 

e^i 

12 

9 

L 

^ 

P 

°T^ 

^J 

Limestone  or  Sandstone 

16 

10 

c 

Sfe 

"^». 

a? 

^jx 

? 

24 

11 

Concrete  (Monolithic) 

These  figures  may  be  used  with  sufficient 

6 
10 

12 
13 

accuracy  for   concrete   walls   with   stucco 

16 

14 

"^        -N, 

v."j£ 

•  ( 

exterior  finish. 

20 

15 

9 

0. 

^  ' 

: 

6 

16 

„• 

0 

Cinder  (Monolithic) 

Conductivity  k  ~>  4.36 

10 
16 

17 
18 

y 

9 

:•' 

~A 

20 

19 

-••••. 

••»•!. 

•" 

*f 

6 

20 

••I^J^- 

Haydite  (Monolithic) 

10 

21 

Conductivity  k  =  3.96 

16 

22 

20 

23 

Cinder  Blocks 

8 

24 

Cores  filled  with  dry  cinders,  69.7  Ib  per  cu  ft. 
Cores  filled  with  granulated  cork,  5.12  Ib 

8 

25 

per  cu  ft. 

8 

26 

Cores  filled  with  rock  wool,  14.2  Ib  per  cu  ft. 
Based  on  one  air  cell  in  direction  of  heat  flow. 
Cores  filled  with  granulated  cork,  5.24  Ib  per 

8 
12 

27 
28 

4^> 

*-^ 

\ 

cu  ft. 
Concrete  Blocks 

12 

29 

8 

30 

a»- 

^ 

\ 

Cores  filled  with  granulated  cork,  5.14  Ib  per 

=35333 

SSE 

"•53S. 

* 

y 

cuft. 

8 

31 

**** 

"-^ 

C 

/ 

Or 

Based  on  one  air  cell  in  direction  of  heat  flow. 

12 

32 

•—•l^ 

Haydite  Blocks 

8 

33 

Cores  filled  with  granulated  cork,  5.06  Ib  per 

cuft. 

8 

34 

Haydite  Blocks 

12 

35 

Cores  filled  with  granulated  corkr  5.6  Ib  per 

cu  ft. 

12 

36 

•Computed  from  factors  marked  by  *  in  Table  2. 
*Based  on  the  actual  thickness  of  2-in.  furring  strips. 

104 


CHAPTER  5,   HEAT  TRANSMISSION  COEFFICIENTS  AND  TABLES 


INTERIOR  FINISH 


UNINSULATED  WALLS 

INSULATED  WALLS 

Plain  walls  —  no  in- 
terior finish 

g 

S" 
3 

II 

1 

§1 

5J2 

'"'"'.3 

§•*•» 
O 

!l! 

S-P.S 

Decorated  building 
board  (M  in.)  with- 
out plaster—  furred 

§"•$« 
^ 

-S  o 

§£. 

Si"! 

g?3 

3s| 

lib 

I1s5 

si  in* 

-dlf^S 
*l*89*3 

j^y 

Pi  S-2«J2«\o"3 

Plaster  on  metal 
lath  attached  to  fur- 
ring strips  (2  in.*)— 
rock  wool  fill  (155 
in.&)« 

gjp.si.1 
52  till  1 
llsSiJI 

A 

B 

C 

D 

E 

F 

G 

H 

I 

J 

K 

L 

0.50 
0.36 
0.28- 

0.46 
0.34 
0.27 

0.30 
0.24 
0.20 

0.32 
0.25 
0.21 

0.30 
0.24 
0.20 

0.23 
0.19 
0.17 

0.22 
0.19- 
0-16- 

0.16 
0.14 
0.13 

0.14 
0.12 
0.11 

0.23 
0.19 
0.17 

0.12 
0.11 
0.10 

0.20 
0.17 
0.15 

0.40 
0.39 
0.30 
0.25 

0.38 
0.37 
0.29 
0.24 

0.26 
0.26 
0.22 
0.19 

0.28 
9.27 
0.22 
0.19 

0.26 
0.26 
0.22 
0.19 

0.20 
0.20 
0.17 
0.16 

0.20 
0.19 
0.17 
0.15 

0.15 
0.15 
0.14 
0.12 

0.13 
0.13 
0.12 
0.11 

0.20 
0.20 
0.18 
0.16 

0.11 
0.11 
0.10 
0.097 

0.18 
0.18 
0.16 
0.14 

0.71 
0.58 
0.49 
0.37 

0.64 
0.53 
0.45 
0.35 

0.37 
0.33 
0.30 
0.25 

0.39 
0.34 
0.31 
0.26 

0.37 
0.33 
0.30 
0.25 

0.26 
0.24 
0.22 
0.20 

0.25 
0.23 
0.22 
0.19 

0.18 
0.17 
0.16 
0.15 

0.15 
0.14 
0.14 
0.13 

0.26 
0.24 
0.22 
0.20 

0.13 
0.13 
0.12 
0.11 

0.23 
0.21 
0.20 
0.18 

0.79 
0.62 
0.48 
0.41 

0.70 
0.57 
0.44 
0.39 

0.39 
0.34 
0.29 
0.27 

0.42 
0.37 
0.31 
0.28 

0.39 
0.34 
0.29 
0.27 

0.27 
0.25 
0.22 
0.21 

0.26 
0.24 
0.21 
0.20 

0.19 
0.18 
0.16 
0.15 

0.16 
0.15 
0.14 
0.13 

0.27 
0.25 
0.22 
0.21 

0.13 
0.13 
0.12 
0.12 

0.23 
0.22 
0.20 
0.18 

0.46 
0.33 
0.22 
0.19 

0.43 
0.31 
0.22 
0.18 

0.29 
0.23 
0.17 
0.15 

0.30 
0.24 
0.18 
0.15 

0.29 
0.23 
0.17 
0.15 

0.22 
0.18 
0.15 
0.13 

0.21 
0.18 
0.14 
0.13 

0.16 
0.14 
0.12 
0.11 

0.14 
0.12 
0.10 
0.09 

0.22 
0.18 
0.15 
0.13 

0.12 
0.11 
0.09 
0.09 

0.19 
0.16 
0.13 
0.12 

0.44 
0.30 
0.21 
0.17 

0.41 
0.29 
0.20 
0.17 

0.28 
0.22 
0.16 
0.14 

0.29 
0.23 
0.17 
0.14 

0.28 
0.22 
0.16 
0.14 

0.21 
0.17 
0.14 
0.12 

0,21 
0.17 
0.14 
0.12 

0.16 
0.14 
0.11 
0.10 

0.13 
0.12 
0.10 
0.09 

0.21 
0.18 
0.14 
0.12 

0.12 
0.10 
0.09 
0.08 

0.19 
0.16 
0.13 
0.11 

0.42 
0.31 

0.39 
0.29 

0.27 
0.23 

0.28 
0.23 

0.27 
0.22 

0.21 

0.18 

0.20 
0.17 

0.16 
0.14 

0.13 
0.12 

0.21 
0.18 

0.12 
0.11 

0.19 
0.16 

0.22 
0.23 
0.37 

0.21 
0.22 
0.35 

0.17 
0.19 
0.25 

0.18 
0.18 
0.26 

0.17 
0.18 
0.25 

0.14 
0.15 
0.19 

0.14 
0.14 
0.19 

0.12 
0.12 
0.15 

0.11 
0.10 
0.13 

0.14 
0.15 
0.19 

0.09 
0.09 
0.11 

0.13 
0.14 
0.17 

0.20 

0.19 

0.17 

0.16 

0.16 

0.13 

0.13 

0.11 

0.10 

0.14 

0.09 

0.13 

0.56 

0.52 

0.32 

0.34 

0.32 

0.24 

0.23 

0.17 

0.14 

0.24 

0.12 

0.21 

0.41 
0.49 

0.39 
0.46 

0.27 
0.30 

0.28 
0.32 

0.27 
0.30 

0.21 
0.23 

0.20 
0.22 

0.15 
0.16 

0.13 
0.14 

0.21 
0.23 

0.12 
0.12 

0.18 
0.20 

0.36 

0.34 

0.26 

0.26 

0.24 

0.19 

0.19 

0.15 

0.13 

0.19 

0.11 

0.17 

0.18 

0.17 

0.15 

0.15 

0.14 

0.13 

0.12 

0.10 

0.09 

0.13 

0.08 

0.12 

0.34 

0.32 

0.25 

0.25 

0.24 

0.19 

0.18 

0.14 

0.12 

0.19 

0.11 

0.17 

0.15 

0.14 

0.13 

0.13 

0.12 

0.11 

0.11 

0.09 

0.08 

0.11 

0.08 

0.10 

eA  waterproof  membrane  should  be  provided  between  the  outer  material  and  the  insulation  fill  to 
prevent  possible  wetting  by  absorption  and  a  subsequent  lowering  of  efficiency. 

105 


HEATING  VENTILATING   AIR  CONDITIONING   GUIDE  1938 


TABLE  4.   COEFFICIENTS  OF  TRANSMISSION  (Z7)  OF  MASONRY  WALLS 
WITH  VARIOUS  TYPES  OF  VENEERS* 


Coefficients  are  expressed  in  Blu  per  hour  per  square  foot  per  degree 
Fahrenheit  difference  in  temperature  between  the  air  on  the  two  sides, 
and  are  based  on  a  wind  velocity  of  Iff  mph. 


TYPE  OF  WALL 


TYPICAL 
CONSTRUCTION 


BACKING 


WALL 

No. 


6  in. 


4  in.  Brick  Veneer* 


Hollow  THe* 


12  in. 


4  in.  Brick  Veneer* 


6  in. 
10  in.  Concrete 

16  in. 


8  in.  Cinder  Blocks 

8  in.  Cinder  Blocks  —  Cores 

filled   with    granulated  cork, 

5.12  Ib  per  cu  ft. 
12  in.  Cinder  Blocks 
12  in.  Cinder    Blocks  —  Cores 
filled   with    granulated    cork, 
5.24  Ib  per  cu  ft. 


4  in.  Brick  Veneer* 


8  in.  Concrete  Blocks 

8  in.  Concrete  Blocks — Cores 

filled   with  granulated   cork, 

5.14  Ib  per  cu  ft. 
12  in.  Concrete  Blocks 

8  in.  Haydite  Block 

8  in.  Haydite    Block— Cores 

filled   with  granulated   cork, 

5.06  Ib  per  cu  ft. 
12  in.  Haydite  Block 
12  in.  Haydite    Block— Cores 

filled   with   granulated    cork, 

5.6  per  cu  ft. 


4  in.  Cut-Stone  Veneer* 


Sin. 

12  in.  Common  Brick 
16  in. 


6  in. 


4  in.  Cut-Stone  Veneer1 


Hollow  me* 


12  in. 


4  in.  Cut-Stone  Veneer1 


6  in. 
10  in.  Concrete 

16  in. 


37 
38 
39 
40 


41 
42 
43 


44 


45 
46 


47 


48 


49 
50 
51 


52 
53 


54 


55 
56 

57 


58 
59 
60 
61 


62 
63 
64 


puted  from  factors  marked  by  *  in  Table  2. 

d  on  the  actual  thickness  of  2-in.  furring  strips. 

<The  6-in.,  8-in.  and  10-in.  tile  figures  are  based  on  two  cells  in  the  direction  of  heat  flow.    The  12-in. 
tHe  is  based  on  three  cells  in  the  direction  of  heat  flow. 


CHAPTER  5.   HEAT  TRANSMISSION  COEFFICIENTS  AND  TABLES 


INTERIOR  FINISH 


UNINSULATED  WALLS 

INSULATE)  WALLS 

i 

.5  S 

§ 

3 

3 

If 

g| 

S3i 

g-g 

3 
ii 

PU  8 

gg 

li-p 

ill 

No  plaster  —  deco- 
rated rigid  or  build- 
ing board  interior 
finish  (ft  in.)- 
furred 

§S 

1 

1 

*§•«  1 

|:§3 

Plaster  (J$  in.)  on 
cork  board  (1H  in.) 
setincementmortar 
(H  in.) 

11  sill 

Sj-slfll 

§lt| 

3i*Jk 

aSif-* 

j|jJ5g 

slssa 

Plaster  (H  in.)  on 
metal  lath  attached 
to  furring  stripe 
(2  in.*)—  flexible  in- 
eulation  (H  in.)  be- 
tween furring  strips 
(one  air  space) 

A 

B 

C 

D 

£ 

F 

G 

H 

I 

J 

K 

L 

0.36 
0.34 
0.34 
0.27 

0.34 
0.33 
0.32 
0.26 

0.24 
0.24 
0.23 
0.20 

0.25 
0.25 
0.24 
0.21 

0.24 
0.24 
0.23 
0.20 

0.19 
0.19 
0.19 
0.16 

0.19 
0.18 
0.18 
0.16 

0.16 
0.14 
0.14 
0.13 

0.13 
0.12 
0.12 
0.11 

0.19 
0.19 
0.19 
0.16 

0.11 
0.11 
0.11 
0.10 

0.17 
0.17 
0.17 
0.15 

0.57 
0.48 
0.39 

0.53 
0.45 
0.37 

0.33 
0.30 
0.26 

0.35 
0.31 
0.27 

0.33 
0.30 
0.26 

0.24 
0.22 
0.20 

0.23 
0.22 
0.19 

0.17 
0.16 
0.15 

0.14 
0.14 
0.13 

0.24 
0.22 
0.20 

0.13 
0.12 
0  11 

0.21 
0.20 
0.18 

0.35 

0.33 

0.24 

0.25 

0.24 

0.19 

0.18 

0.14 

0.12 

0.19 

0.11 

0.17 

0.20 
0.31 

0.19 
0.30 

0.16 
0.22 

0.16 
0.23 

0.16 
0.22 

0.13 
0.18 

0.13 
0.17 

0.11 
0.14 

0.10 
0.12 

0.13 
0.18 

0.09 
0.11 

0.12 
0.16 

0.18 

0.18 

0.15 

0.15 

0.15 

0.13 

0.12 

0.10 

0.09 

0.13 

0.08 

0.12 

0.44 

0.42 

0.28 

0.30 

0.28 

0.21 

0.21 

0.16 

0.13 

0.21 

0.12 

0.19 

0.34 
0.40 
0.31 

0.32 
0.38 
0.29 

0.24 
0.26 
0.23 

0.25 
0.28 
0.23 

0.23 
0.26 
0.22 

0.19 
0.20 
0.18 

0.18 
0.20 
0.17 

0.14 
0.15 
0.14 

0.12 
0.13 
0.12 

0.19 
0.20 
0.18 

0.11 
0.11 
0.11 

0.17 
0.18 
0.16 

0.17 
0.29 

0.16 
0.28 

0.14 
0.21 

0,14 
0.22 

0.14 
0.21 

0.12 
0.17 

0.12 
0.17 

0.10 
0.13 

0.09 
0.12 

0.12 
0.17 

0.08 
0.10 

0.11 
0.16 

0.14 

0.14 

0.12 

0.12 

0.12 

0.10 

0.10 

0.09 

0.08 

0.10 

0.07 

0.10 

0.37 
0.28 
0.23 

0.35 
0.27 
0.22 

0.25 
0.21 
0.18 

0.26 
0.21 
0.18 

0.25 
0.21 
0.18 

0.19 
0.17 
0.15 

0.19 
0.16 
0.14 

0.15 
0.13 
0.12 

0.13 
0.12 
0.11 

0.19 
0.17 
0.15 

0.11 
0.10 
0.095 

0.17 
0.15 
0.14 

0.37 
0.36 
0.35 
0.28 

0.35 
0.34 
0.33 
0.26 

0.25 
0.24 
0.24 
0.20 

0.26 
0.25 
0.25 
0.21 

0.25 
0.24 
0.24 
0.20 

0.20 
0.19 
0.19 
0.17 

0.19 
0.19 
0.18 
0.16 

0.15 
0.15 
0.14 
0.13 

0.13 
0.13 
0.12 
0.11 

0.20 
0.19 
0.19 
0.17 

0.11 
0.11 
0.11 
0.10 

0.18 
0.17 
0.17 
0.15 

0.61 
0.51 
0.41 

0.56 
0.47 
0.38 

0.34 
0.31 
0.26 

0.36 
0.32 
0.28 

0.34 
0.31 
0.26 

0.25 
0.23 
0.20 

0.24 
0.22 
0.20 

0.18 
0.17 
0.15 

0.15 
0.14 
0.13 

0.25 
0.23 
0.21 

0.13 
0.12 
0.11 

0.22 
0.20 
0.18 

'Calculations  include  cement  mortar  (H  in.)  between  veneer  or  facing  and  backing. 
'Based  on  one  air  cell  in  direction  of  heat  now. 

/A  waterproof  membrane  should  be  provided  between  the  outer  material  and  the  insulation  fill  to 
prevent  possible  wetting  by  absorption  and  a  subsequent  lowering  of  efficiency. 

107 


HEATING  VENTILATING  AIR  CONDITIONING  GUIDE  1938 


TABLE  5.   COEFFICIENTS  OF  TRANSMISSION  (27)  OF 
VARIOUS  TYPES  OF  FRAME  CONSTRUCTION* 


These  coefficients  ere  expressed  in  Btu  per  hour  per  square  foot  per 
degree  Fahrenheit  difference  in  temperature  between  the  air  on  the  two 
sides,  and  are  based  on  a  wind  velocity  of  15  mph. 


TYPICAL 
CONSTRUCTION 

i 

'.          EXTERIOR  FINISH 

i 

TYPE  OF  SHEATHING 

WALL 
No. 

rssT^fi 

^ 

LJO^?; 

^/Hfcvr 

/WIVV       J; 

U* 

/HtAT 

"i  ijr  "^** 

/HEAT 
/WA 

/Kt« 

i 

1 

K"  JM 

MHG. 

*80£ 

ttiHCi 

•HWG 
TtK< 

P 

KING 
>UC1 

1 

rx 

KIKS 

«•, 

1 

1 
J/. 

r 

\ 

1 

\ 

c.\ 

> 

Wood  Siding  or  Clapboard 

1  in.  Wood* 

65 

2%2  in-  Rigid  Insulation 

66 

^  in.  Plaster  Board 

67 

Wood  Shingles 

1  in.  Wood* 

68 

%  in.  Rigid  Insulation* 

69 

%  in.  Plaster  Board* 

70 

Stucco 

1  in.  Wood* 

71 

2%2  in.  Rigid  Insulation 

72 

M  in.  Plaster  Board 

73 

Brick/  Veneer 

1  in.  Wood* 

74 

%  in.  Rigid  Insulation 

75 

}i  in.  Plaster  Board 

76 

"Computed  from  factors  marked  by  *  in  Table  2. 
plaste?  board^0"**8  ^^  ^  be  ^^  ^^  sufficient  accuracy  for  plaster  on  wood  lath  or  plaster  on 
•Based  on  the  actual  width  of  2  by  4-in.  studding,  namely,  35i  in. 


108 


CHAPTER  5.   HEAT  TRANSMISSION  COEFFICIENTS  AND  TABLES 


INTERIOR  FINISH 


No  INSULATION*  BETWEEN  STUDDING 


INSULATION  BETWEEN  STUDDING 


I 

5 
5 
J3 

3 

i 

5 

J3 
J 

g 

S 
» 

if 

II 

1 

•a 
«» 

ll 

& 
Is 

Plaster  (^  in.)  on  rigid  insulation 
(H  in.)  on  studding 

i 

~i 
s! 

0 

|3 

Plaster  tt£  in.)  on  corkboard  UH  in.) 
on  studding 

No  piaster  —  decorated  rigid  or  build- 
ing board  interior  finish  (J-a  in.) 

1  in.  wood  sheathing,1*  furring  strips, 
plaster  (H  in.)  on  wood  lath 

!.- 

ji 

o  o 

3-!s 

SJi 

£  tt_g 

Plaster  (£4  m.)  on  metal  lath*  on 
studding  —  flexible  insulation  (?£  in.) 
between  studding  and  in  contact  with 
sheathing 

§3 

5|  | 

«* 

B.ST 

c^i 

.111 

gr* 

*-.s| 
ill 

PH^aJS 

Plaster  (H  in.)  on  metal  lathh  on 
studding  —  flexible  insulation  (1  in.) 
between  studding  —  2  air  spaces 

Plaster  (£4  in.)  on  metal  lathfc  on 
studding—  rock  wool  fill  (3fi«  in.c) 
between  studding"* 

A 

B 

c 

D 

E 

F 

G 

H 

I 

J 

K 

L 

M 

0.25 

0.26 

0.25 

0.19 

0.15 

0.11 

0.19 

0.17 

0.20 

0.17 

0.15 

0.12 

0.072 

0.23 

0.24 

0.23 

0.18 

0.14 

0.11 

0.18 

0.14 

0.19 

0.17 

0.13 

0.10 

0.070 

0.31 

0.33 

0.31 

0.22 

0.17 

0.13 

0.23 

•  0.19 

0.24 

0.20 

0.17 

0.13 

0.076 

0.25 

0.26 

0.25 

0.19 

0.15 

0.11 

0.19 

0.17 

0.20 

0.17 

0.15 

0.12 

0.072 

0.19 

0.20 

0.19 

0.15 

0.12 

0.10 

0.16 

0.14 

0.16 

0.14 

0.11 

0.094 

0.066 

0.24 

0.25 

0.24 

0.19 

0.15 

0.11 

0.19 

0.19 

0,19 

0.17 

0.15 

0.12 

0.071 

0.30 

0.31 

0.30 

0.22 

0.16 

0.12 

0.22 

0.19 

0.23 

0.20 

0.17 

0.13 

0.076 

0.27 

0.29 

0.27 

0.20 

0.16 

0.12 

0.21 

0.15 

0.22 

0.19 

0.14 

0.11 

0.074 

0.40 

0.43 

0.40 

0.26 

0.19 

0.14 

0.28 

0.22 

0.29 

0.24 

0.20 

0.14 

0.081 

0.27 

0.28 

0.27 

0.20 

0.15 

0.12 

0.21 

0.17 

0.21 

0.18 

0.16 

0.12 

0.074 

0.25 

0.26 

0.25 

0.19 

0.15 

0.11 

0.19 

OJL5 

0.20 

0.18 

0.13 

0.11 

0.072 

0.35 

0.37 

0.35 

0.24 

0.18 

0.13 

0.25 

0.21 

0.26 

0.22 

0.18 

0.14 

0.079 

*Yellow  pine  or  fir — actual  thickness  about  %  in. 
•Furring  strips  between  wood  shingles  and  sheathing. 

/Small  air  space  and  mortar  between  building  paper  and  brick  veneer  neglected. 

»A  waterproof  membrane  should  be  provided  between  the  outer  material  and  the  insulation  fill  to 
prevent  possible  wetting  by  absorption  and  a  subsequent  lowering  of  efficiency. 
AStud  and  rock  wool  fill  areas  combined. 


109 


HEATING  VENTILATING   AIR  CONDITIONING   GUIDE  1938 


TABLE  6.    COEFFICIENTS  OF  TRANSMISSION  (U)  OF  FRAME  INTERIOR  WALLS 
AND  PARTITIONS** 

Coefficients  are  expressed  in  Btu  per  hour  per  square  foot  per  degree  Fahrenheit  difference  in  temperature 
between  the  air  on  the  two  sides,  and  are  based  on  still  air  (no  wind)  conditions  on  both  sides. 


TYPICAL  CONSTRUCTION 

WALL 
No. 

SINGLE 
PARTITION 
(FINISH 
ON  ONE 
SIDE  OF 
STUDDING) 

DOUBLE  PARTITION 
(FINISHED  ON  BOTH  SIDES  OP  STUDDING) 

Air 
Space 
Between 
Studding 

Flaked 

Gffi* 
Between 
Studding 

Rock 
Wool 
Fill* 
Between 
Studding 

'Menble 
Insulation 
Between 
Studding 
(One  Air 
Space) 

Stud  Space  Faced 
One     Side     with 
Bright  Aluminum 
Foil 

TYPE  OF  WALL 

A 

B 

C 

D 

E 

F 

Wood  Lath  and  Plaster 
On  Studding 

77 

0.62 

0.34 

0.11 

0.076 

0.21 

0.24 

Metal  Lath  and  Plaster* 

On  Studding 

78 

0.69 

0.39 

0,11 

0.078 

0.23 

0.26 

Plaster  Board  (%  in.)  and 
Plaster*  On  Studding 

79 

0.61 

0.34 

0.10 

0.075 

0.21 

0.24 

M  in.  Rigid  Insulation  and 
Plaster*  On  Studding 

80 

0.35 

0.18 

0.083 

0.063 

0.14 

0.15 

1  in.  Rigid  Insulation  and 
Plaster*  On  Studding 

81 

0.23 

0.12 

0.066 

0.054 

0.097 

0.10 

1H  in.  Corkboard  and 
Plaster*  On  Studding 

82 

0.16 

0.081 

0..052 

0.044 

0.070 

0.073 

2  in.  Corkboard  and 
Plaster*  On  Studding 

83 

0.12 

0.063 

0.045 

0.038 

0.057 

0.059 

•Computed  from  factors  marked  by  *  in  Table  2.       'Plaster  on  metal  lath  assumed  %-in.  thick. 
*Thickness  assumed  3^  inu  'Plaster  assumed  H-in-  thick. 


TABLE  7.    COEFFICIENTS  OF  TRANSMISSION  (27)  OF  MASONRY  PARTITIONS^ 

Coefficients  are  expressed  in  Btu  per  hour  per  square  foot  per  degree  Fahrenheit  difference  in  temperature 
between  the  air  on  the  two  sides,  and  are  based  on  still  air  (no  wind)  conditions  on  both  sides. 


TYPICAL  CONSTRUCTION 

W*S^^^ 

r 

WALLS 

WALLS 

I 

No. 

PLAIN  WALLS 
(No  PLASTER) 

PLASTERED 
ON  ONE  SIDE 

PLASTERED 
ON  BOTH  SIDES 

TYPE  OF  WALL 

A 

B 

C 

4-in.  Hollow  Clay  Tile 
4-in.  Common  Brick 

84 
85 

0.45 
0.50 

0.42 
0.46 

0.40 
0.43 

4-in.  Hollow  Gypsum  Tile 

86 

0.30 

0.28 

0.27 

2-in.  Solid  Plaster 

87 





0.53 

•Computed  from  factors  marked  by  *  in  Table  2. 

110 


CHAPTER  5.   HEAT  TRANSMISSION  COEFFICIENTS  AND  TABLES 


a)     o 

g  a 

« 


U    .v. 

§•3 
^ 


U,  | 

I  Is 

G  sh 

P  rj 


«« 
S^ 


%    B 


per 
are 


NTS 

per  hour 
and 


8.  COEFF 
e  expressed  in 


I 


(% 


s 


2i§j5 


§ 


H 


s 


.2 
1 


factors  marked 
ed  to  be  %  in. 
ed  to  be  %  in. 


21! 
|i! 

8 


'55 


u,  d  fl 
.3  cs  o 

»1 


111 


HEATING  VENTILATING  AIR  CONDITIONING   GUIDE  1938 


« 3 
8:  1 

fc 


o 


li1 
IP 


4§5i 
5lii-i 

~a3ai 


oooo    oooo 


"Iff 

ml 


gg§       .S( 

ill  gllc! 
^^^     s 


!| 

!4E 


I 


ooaoooo 

ClP-lpHrH 


3 

B 

i 


^«8 

fea 


|? 
1§ 


g.S 
&^ 


#  CO  CO  CO 


3 


•3 

I 


S    S 

|   f 
I   I 


11 

s§ 

03 

l§ 

I 

11 
33 

^s 


H  w  3  »  a 

!*!! 


112 


CHAPTER  5.   HEAT  TRANSMISSION  COEFFICIENTS  AND  TABLES 


to    "5 


g    1-J 

O     — ;j 

o  i! 


(3 


stl 

i! 


§    -S 


o    1 
1-1    o 

w 
j 

PQ 


If 


^1'^ 

:^|p 


=1 

•Cffl 


§2 


O        CO        iH        1H 
rl       r-t       T-<       tH 

0      0      0      0 


0      O      0      0 


^j     w     g     g 
o*     o"     o     o 


0000 


0000 


3   3    T) 

s  a  a 

)H        M          0 


B     a    .2    .3 


*! 

il 


l 

•s 


I     11 

a        si 

32 
§  ,44  .*<    .  «  ** 

JMIfl 

I***}? 


puted 
med 
med 
med  1 
figures 
rete. 


113 


HEATING  VENTILATING   AIR  CONDITIONING   GUIDE  1938 


TABLE  11.    COEFFICIENTS  OF  TRANSMISSION  (U)  OF  VARIOUS  TYPES 
OF  FLAT  ROOFS  COVERED  WITH  BUILT-UP  ROOFING* 


TYPICAL  CONSTRUCTION 


WITHOUT  CEILINGS 


WITH  METAL  LATH 

AND 
PLASTER  CEILINGS* 


TYPE  OF  ROOF  DECK 


THICKNESS 

OF 

ROOF 
DECK 

(INCHES) 


No. 


Precast  Cement  Tile 


Concrete 
Concrete 
Concrete 


m 


Wood 
Wood 
Wood 
Wood 


1* 

& 

4» 


Gypsum  Fiber  Concrete0 
(2  in.)  on  Plaster  Board 
(Mm.) 

Gypsum  Fiber  Concrete* 
(3  in.)  on  Plaster  Board 


Gypsum  Fiber  Concrete* 
(2  in.)  on  Rigid  Insula- 
lation  Board  (H  in.) 

Gypsum  Fiber  Concrete* 
(2  in.)  on  Rigid  Insula- 
tion Board  (1  in.) 


10 


12 


Flat  Metal  Roofs 

Coefficient  of  transmis- 
sion of  bare  corrugated 
iron  (no  roofing)  is  1.50 
Btu  per  hour  per  square 
foot  of  projected  area  per 
degree  Fahrenheit  dif- 
ference in  temperature, 
based  on  an  outside  wind 
velocity  of  15  mph. 


13 


•Computed  from  factors  marked  by  *  in  Table  2. 

^Nominal  thicknesses  specified — actual  thicknesses  used  in  calculations. 

•Gypsum  fiber  concrete- -87}$  per  cent  gypsum,  12H  per  cent  wood  fiber. 


114 


CHAPTER  5.  HEAT  TRANSMISSION  COEFFICIENTS  AND  TABLES 


Coefficients  are  expressed  in  Btu  per  hour  per  square  foot  per  degree 
Fahrenheit  difference  in  temperature  between  the  air  on  the  two  sides, 
and  are  based  on  an  outside  wind  velocity  of  15  mph. 


WITHOUT  CEILING—  UNDER  SIDE  OF 
ROOF  EXPOSED 

WITH  METAL  LATH  AND 
PLASTER  CEILINGS* 

No  Insulation 

I 

3 

2 

3 

2 

.2 

c*> 

1 
I 

3 

5 

.? 

EJ 

es 

3 

1 

CM 

| 

1 

i 

a 

} 

| 

S 

.5 
^ 

j 

1 

1 
1 

1 

0 

A 

B 

c 

D 

E 

F 

G 

H 

I 

j 

K 

L 

M 

N 

0 

P 

0.84 

0.37 

0.24 

0.18 

0.14 

0.22 

0.16 

0.13 

0.43 

0.26 

0.19 

0.15 

0.12 

0.18 

0.14 

0.11 

0.82 
0.72 
0.64 

0.37 
0.34 
0.33 

0.24 
0.23 
0.22 

0.17 
0.17 
0.16 

0.14 
0.13 
0.13 

0.22 
0.21 
0.21 

0.16 
0.16 
0.15 

0.13 
0.12 
0.12 

0.42 
0.40 
0.37 

0.26 
0.25 
0.24 

0.1Q 
0.18 
0.18 

0.15 
0.14 
0.14 

0.12 
0.12 
0.11 

0.18 
0.17 
0.17 

0.14 
0.13 
0.13 

0.11 
0.11 
0.11 

0.49 
0.37 
032 
0.23 

0.28 
0.24 
0.22 
0.17 

0.20 
0.18 
0.16 
0.14 

0.15 
0.14 
0.13 
0.11 

0.12 
0.11 
0.11 
0.096 

0.19 
0.17 
0.16 
0.13 

0.14 
0.13 
0.12 
0.11 

0.12 
0.11 
0.10 
0.091 

0.32 
0.26 
0.24 
0.18 

0.21 
0.19 
0.17 
0.14 

0.16 
0.15 
0.14 
0.12 

0.13 
0.12 
0.11 
0.10 

0.11 
0.10 
0.097 
0.087 

0.15 
0.14 
0.13 
0.11 

0.12 
0.11 
0.11 
0.096 

0.10 
0.095 
0.092 
0.082 

0.40 
0.32 
0.26 
0.19 

0.25 
0.22 
0.19 
0.15 

0.18 
0.16. 
0.15 
0.12 

0.14 
0.13 
0.12 
0.10 

0.12 
0.11 
0.10 
0.09 

0.17 
0.15 
0.14 
0.12 

0.13 
0.12 
0.11 
0.10 

0.11 
0.10 
0.10 
0.08 

0.27 
0.23 
0.20 
0.16 

0.19 
0.17 
0.16 
0.13 

0.15 
0.14 
0.13 
0.11 

0.12 
0.11 
0.11 
0.09 

0.10 
0.097 
0.09 
0.08 

0.14 
0.13 
0.12 
0.10 

0.12 
0.11 
0.10 
0.09 

0.097 
0.091 
0.087 
0.077 

0.95 

0.39 

0.25 

0.18 

0.14 

0.23 

0.17 

0.13 

0.46 

0.27 

0.19 

0.15 

0.12 

0.18 

0.14 

0.11 

dThese  coefficients  may  be  used  with  sufficient  accuracy  for  wood  lath  and  plaster,  or  plaster  board  and 
plaster  ceilings.  It  is  assumed  that  there  is  an  air  space  between  the  under  side  of  the  roof  deck  and  the 
upper  side  of  the  ceiling. 


115 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


£  Ii 
§  •!' 


5    28 

O      3fB 


1 
If 


.11 

il 

»-t      o>o 

y  Is 

3  f1 

a  i 
|  | 

^  "i 


pn*  (-ui  z)  pjsoqaijoo 


(til 


P»JH 


J^SBU  pn*  qjiq  poo^ 


(•m^pjeoajajreij 


j^sBUptre^Bn^api 


ilslgii 


I    I, 


o  I  o     o     o 


B    «    - 
;  o     o 


F  RO 
AND 


PICAL 
RUCTION 


CO 


% 


^ 


! 
-  i 

»i 


i « 

llii 

|  sis 

•s    -a  a  c 

s  fi* 
s  sss 

"  ^I-s    - 
I  152  I 


ci 


^3*8 

Hs 


^     a«? 
•3    §3!    3 

^3-SI  2 

an 

-a  aosts  c^«5 

laSI-Si' 

S.9a-g«-!  u 

^•sj-s? 

I-SgS^l 
l^|3 

a^olo^, 

^issss 

31-1  S"SCO  ho14-1 

l§1iiil 

3|sf|w| 


§ 


116 


CHAPTER  5.   HEAT  TRANSMISSION  COEFFICIENTS  AND  TABLES 


TABLE  13.    COEFFICIENTS  OF  TRANSMISSION  (£7)  OF  DOORS,  WINDOWS,  SKYLIGHTS 

AND  GLASS  WALLS 

Coefficients  are  based  on  a  wind  velocity  of  15  mph,  and  are  expressed  in  Biu  per  hour  per  square  foot  per 
degree  Fahrenheit  difference  in  temperature  between  the  air  inside  and  outside  of  the  door,  window,  skylight  or  watt 

^ A .  Windows  and  Skylights 

DESCRIPTION  '  L" 


Single.- 

Double-- 
Triple.-  


0.45* 


B.  Solid  Wood  Doors*>, 


NOMINAL 
THICKNESS 
INCHES 

ACTUAL 
THICKNESS                                                     U 
INCHES 

1 

% 

0.69 

1/4 

1K6                             ;                0.59 

1% 

liKs 

0.52 

\% 

IN 

0.51 

2 

i« 

0.46 

2Ji 

2N                              ;                0.38 

3 

25i 

0.33 

C.    Glass  Walls 


DESCRIPTION 

17 

Hollow  glass  tile  wall,  6  x  6  x  2  in.  thick  blocks 
Wind  velocity  15  mph,  outside  surface;  still  air,  inside  surface.-... 
Still  air,  outside  and  inside  surface. 

0.60 
0.48 

«See  Heating,  Ventilating  and  Air  Conditioning,  by  Harding  and  Willard,  revised  edition,  1932. 

^Computed  using  C  =  1.15  for  wood;  /i  -  1.65  and/0  =  6.0. 

"It  is  sufficiently  accurate  to  use  the  same  coefficient  of  transmission  for  doors  containing  thin  wood 
panels  as  that  of  single  panes  of  glass,  namely,  1.13  Btu  per  hour  per  square  foot  per  degree  difference 
between  inside  and  outside  air  temperatures. 

it  is  probable  that  the  values  of  U  for  these  two  types  of  roofs  will 
compare  favorably. 

The  thicknesses  upon  which  the  coefficients  in  Tables  3  to  13,  inclusive, 
are  based  are  as  follows: 


Brick  veneer 

Plaster  and  metal  lath.. 


4      in. 
Kin. 


Plaster  (on  wood  lath,  plasterboard,  rigid  insulation,  board 

form,  or  corkboard) 

Slate  (roofing) 

Stucco  on  wire  mesh  reinforcing 

Tar  and  gravel  or  slag-surfaced  built-up  roofing. 

1-in.  lumber  (S-2-S) 

iH-in-  lumber  (S-2-S) 

2-in.  lumber  (S-2-S)  _„. 

2j^-in.  lumber  (S-2-S).. 

3-in.  lumber  (S-2-S). 

4-in.  lumber  (S-2-S)., 

Finish  flooring  (maple  or  oak)...., 

Solid  brick  walls  are  based  on  4-in.  hard  brick  (high  density)  and  the 
remainder  common  brick  (low  density).  Stucco  is  assumed  to  be  1-in. 
thick  on  masonry  walls.  Where  metal  lath  and  plaster  are  specified,  the 
metal  lath  is  neglected. 

117 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 

The  coefficients  of  transmission  of  the  pitched  roofs  in  Table  12  apply 
where  the  roof  is  over  a  heated  attic  or  top  floor  so  the  heat  passes  directly 
through  the  roof  structure  including  whatever  finish  is  applied  to  the 
underside  of  the  roof  rafters. 

Combined  Coefficients  of  Transmission 

If  the  attic  is  unheated,  the  roof  structure  and  ceiling  of  the  top  floor 
must  both  be  taken  into  consideration,  and  the  combined  coefficient  of 
transmission  determined.  The  formula  for  calculating  the  combined 
coefficient  of  transmission  of  a  top  floor  ceiling,  unheated  attic  space,  and 
pitched  roof,  per  square  foot  of  ceiling  area,  is  as  follows: 

UT  X  £/ce 

U  -    „     ,     tfce  (6) 

Ur  +  ^r 

where 

U  —  combined  coefficient  to  be  used  with  ceiling  area. 
Ur  =  coefficient  of  transmission  of  the  roof. 
£/ce  =  coefficient  of  transmission  of  the  ceiling. 
n  =  the  ratio  of  the  area  of  the  roof  to  the  area  of  the  ceiling. 

Stating  the  formula  in  terms  of  the  total  heat  resistance  of  the  ceiling 
and  roof, 


In  selecting  the  values  to  be  used  for  Ur  and  C/ce  it  should  be  noted 
that  the  under  surface  of  the  roof  and  the  upper  surface  of  the  ceiling  are 
more  nearly  equivalent  to  the  boundary  surfaces  of  an  internal  air  space 
than  they  are  to  the  external  surfaces  of  a  wall.  It  would  be  more  nearly 
correct  to  use  a  value  of  2.2  rather  than  the  usual  value  of  1.65  as  coef- 
ficients for  these  surfaces.  In  most  cases  this  would  make  only  a  minor 
change  in  U.  It  should  be  noted  that  the  over-all  coefficient  should  be 
multiplied  by  the  ceiling  and  not  the  roof  area. 

If  the  unheated  attic  space  between  the  roof  and  ceiling  has  no  dormers, 
windows  or  vertical  wall  spaces  the  combined  coefficients  may  be  used 
for^determining  the  heat  loss  through  the  roof  construction  between  the 
attic  and  top  floor  ceiling.  If  the  unheated  attic  contains  windows  and 
vertical  wall  spaces  these  must  be  taken  into  consideration  in  calculating 
the  roof  area  and  also  its  coefficient  Z7r.  In  this  case  an  approximate 
value  of  Z7r  may  be  obtained  as  the  summation  of  the  coefficient  of  each 
individual  section  such  as  the  roof,  vertical  walls  or  windows  times  its 
percentage  of  total  area.  This  coefficient  may  be  used  with  reasonable 
accuracy  in  the  above  formulae.  If,  however,  there  are  roof  ventilators 
such  that  the  attic  air  is  substantially  at  outside  temperature,  then  the 
roof  should  be  neglected  and  only  the  coefficient  for  the  'top  floor  ceiling 
construction  used. 

Basements  and  Unheated  Rooms 

The  heat  loss  through  floors  into  basements  and  into  unheated  rooms 
kept  closed  may  be  computed  by  assuming  a  temperature  for  these  rooms 

118 


CHAPTER  5.   HEAT  TRANSMISSION  COEFFICIENTS  AND  TABLES 

of  32  F.    Additional  information  on  the  inside  and  outside  temperatures 
to  be  used  in  heat  loss  calculations  is  given  in  Chapter  7. 

REFERENCES 

Effects  of  Air  Velocities  on  Surface  Coefficients,  by  F.  B.  Rowley,  A.  B.  Algren  and 
J.  L.  Blackshaw  (A.S.H.V.E.  TRANSACTIONS,  Vol.  36,  1930}  p.  123). 

Wind  Velocity  Gradients  Near  a  Surface  and  Their  Effect  on  Film  Conductance,  by 
F.  C.  Houghten  and  Paul  McDermott  (A.S.H.V.E.  TRANSACTIONS,  Vol.  37,  1931,  p.  301). 

Insulating  Effect  of  Successive  Air  Spaces  Bounded  by  Bright  Metallic  Surfaces,  by 
L.  W.  Schad  (A.S.H.V.E.  TRANSACTIONS,  Vol.  37,  1931,  p.  285). 

Conductivity  of  Concrete,  by  F.  C.  Houghten  and  Carl  Gutberlet  (A.S.H.V.E. 
TRANSACTIONS,  Vol.  38,  1932,  p.  47). 

Surface  Coefficients  as  Affected  by  Direction  of  Wind,  by  F.  B.  Rowley  and  W.  A. 
Eckley  (A.S.H.V.E.  TRANSACTIONS,  Vol.  38,  1932,  p.  33). 

Importance  of  Radiation  in  Heat  Transfer  Through  Air  Spaces,  by  E.  R.  Queer 
(A.S.H.V.E.  TRANSACTIONS,  Vol.  38,  1932,  p.  77). 

The  Heat  Conductivity  of  Wood  at  Climatic  Temperature  Differences,  by  F.  B. 
Rowley  (A.S.H.V.E.  TRANSACTIONS,  Vol.  39,  1933,  p.  329). 

Insulating  Value  of  Bright  Metallic  Surfaces,  by  F.  B.  Rowley  (A.S.H.V.E.  TRANS- 
ACTIONS, Vol.  40,  1934,  p.  413). 

Thermal  Properties  of  Concrete  Construction,  by  F.  B.  Rowley,  A.  B.  Algren  and 
Clifford  Carlson  (A.S.H.V.E.  TRANSACTIONS,  Vol.  42,  1936,  p.  33). 

Properties  of  Metal  Foil  as  an  Insulating  Material,  by  J.  L.  Gregg  (Refrigerating 
Engineering,  May,  1932). 

Thermal  Insulation  with  Aluminum  Foil,  by  R.  B.  Mason  (Industrial  and  Engineering 
Chemistry,  March,  1933). 

Thermal  Insulation  of  Buildings,  Technical  Paper  No.  11  (American  Architect, 
May,  1934). 

Thermal  Properties  of  Concrete  Construction,  by  F.  B.  Rowley,  A.  B.  Algren  and 
Robert  Lander  (A.S.H.V.E.  JOURNAL  SECTION,  Heating,  Piping  and  Air  Conditioning, 
November,  1936,  p.  621). 

Radiation  and  Convection  Across  Air  Spaces  in  Frame  Construction,  by  G.  B. 
Wilkesand  C.  M.  F.  Peterson  (A.S.H.V.E.  JOURNAL  SECTION,  Heating,  Piping  and  Air 
Conditioning,  August,  1937,  p.  505). 

Heat  Insulation  as  Applied  to  Buildings  and  Structures,  by  E.  A.  Allcut,  University 
of  Toronto,  1934. 

House  Insulation,  Its  Economies  and  Application,  by  Russell  E.  Backstrom  (Report 
of  the  National  Committee  on  Wood  Utilization,  United  States  Government  Printing 
Office,  1931). 

Heat  Transmission  Through  Building  Materials,  by  F.  B.  Rowley  and  A.  B.  Algren, 
University  of  Minnesota  Engineering  Experiment  Station  Bulletin  No.  8. 

Calculation  of  Heat  Transmission,  by  Margaret  Fishenden  and  Owen  A.  Saunders. 

Heating,  Ventilating  and  Air  Conditioning,  by  Harding  and  Willard,  Revised  Edition, 
1932. 

Heat  Transmission,  by  W.  H.  McAdams. 
Industrial  Heat  Transfer,  by  Shack. 

PROBLEMS  IN  PRACTICE 

1  •  What  is  the  coefficient  U  and  how  is  it  applied? 

The  coefficient  U  is  the  heat  loss  through  walls,  ceilings,  and  floors  and  the  value  depends 
upon  the  construction  and  material,  expressed  in  Btu  per  hour  per  square  foot  per  degree 
difference  in  temperature  between  the  inside  and  outside.  To  determine  the  total  heat 
loss,  multiply  U  for  each  material  by  the  square  feet  of  surface  and  the  temperature 
difference. 

119 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

2  •  Find  the  value  of  U  for  a  6-in.  concrete  wall  with  plaster  on  metal  lath 
attached  to  2-in.  furring  strips  with  flanged  J^-in.  blanket  insulation. 

0.23  (Table  3,  Wall  12L). 

3  •  A  wall  is  built  with  two  layers  of  J^-in.  insulating  material  spaced  1  in. 
apart;  the  air  space  is  lined  on  one  side  with  bright  aluminum  foil;  mean 
temperature  is  40  F;  still  air  on  both  sides  of  wall;  k  for  insulating  material 
is  0.34.    Calculate  the  value  of  U. 

fl  =  1.65;  /0  =  1.65;  a  =  0.46 

.       l          ft  397 
"=  6'327 


U  -  -J-  -  0.158 

4  •  What  is  the  inside  surface  temperature  of  a  6-in.  solid  concrete  wall? 
Inside  ah*,  70  F;  outside  air,  -20  F  with  15  mph  wind. 

The  temperature  drop  from  point  to  point  through  a  wall  is  directly  proportional  to  the 
heat  resistance. 

fl  =  1.65;  k  for  concrete  =  12.62  ;/0  =  6.0 
Over-all  resistance  R  =  +  +  JL  .1 


Temperature  drop,  inside  air  to  surface  —  1.65 
Temperature  drop,  air  to  air  1.27 

90 

Temperature  drop,  inside  air  to  surface  =   .,  nfy  „  ,  _g    =  43 

L.£(  X  l.oo 

70  —  43  =  27  F,  inside  surface  temperature  of  wall. 

5  •  How  many  inches  of  insulating  material  having  a  conductivity  of  0.30 
would  be  required,  for  the  wall  of  Question  4,  to  raise  the  inside  surface  tem- 
perature to  60  F? 

Temperature  drop,  air  to  inside  surface  =  10  F;  temperature  drop,  inside  surface  to  out- 
side air  —  80  F.  Therefore,  the  heat  resistance  from  inside  wall  surface  to  outside  air 

must  be  eight  times  that  from  inside  air  to  inside  wall  surface,  or  8  X  -rir-  =  4.85.  The 

1.65 
resistance  for  added  material  is,  therefore, 


485  -  TO  +      =  4-19 

4.19  X  0.30  -  1.25  in.  of  insulation. 

6f,  £-n  unheated  attic  space  in  a  residence  has  an  equivalent  pitched  roof  area 
of  1560  sq  ft  and  a  ceiling  area  of  1200  sq  ft.  If  15  per  cent  of  the  roof  area  is 
composed  of  vertical  wall  spaces  having  a  value  of  U  =  0.52,  determine  the 
total  heat  loss  per  hour  through  the  ceiling  and  roof  for  a  temperature  dif- 
ference of  85  F,  if  U  =  0.46  for  the  roof  and  U  =  0.38  for  the  ceiling. 

An  approximate  value  of  U  for  the  roof  is  equivalent  to  the  summation  of  coefficients 
tor  each  individual  section  times  its  percentage  of  total  area. 

UT  =  (0.52  X  0.15)  -f-  (0.46  X  0.85)  =  0.47. 
Ratio  of  roof  area,  to  ceiling  =  1560  -f-  1200  =  1.3. 
Substituting  in  Formula  6: 

0.47  X  0.38 


H  =  A  U  ft  -  /0)  =  1200  X  0.235  X  85  =  23,900  Btu  per  hour. 

120 


Chapter  6 

AIR  LEAKAGE 

Nature  of  Air  Infiltration,  Infiltration  Through  Walls,  Window 

Leakage,  Door  Leakage,  Selection  of  Wind  Velocity,  Crack 

Length  used  for  Computations,  Multi-Story  Buildings,  Heat 

Equivalent  of  Air  Infiltration 

AIR  leakage  losses  are  those  resulting  from  the  displacement  of  heated 
air  in  a  building  by  unheated  outside  air,  the  interchange  taking 
place  through  various  apertures  in  the  building,  such  as  cracks  around 
doors  and  windows,  fireplaces  and  chimneys.  This  leakage  of  air  must  be 
considered  in  heating  and  cooling  calculations.   (See  Chapters  7  and  8.) 

NATUBE  OF  Am  INFILTRATION 

The  natural  movement  of  air  through  building  construction  is  due  to 
two  causes.  One  is  the  pressure  exerted  by  the  wind;  the  other  is  the 
difference  in  density  of  outside  and  inside  air  because  of  differences  in 
temperature. 

The  wind  causes  a  pressure  to  be  exerted  on  one  or  two  sides  of  a 
building.  As  a  result,  air  comes  into  the  building  on  the  windward  side 
through  cracks  or  porous  construction,  and  a  similar  quantity  of  air 
leaves  on  the  leeward  side  through  like  openings.  In  general  the  resis- 
tance to  air  movement  is  similar  on  the  windward  to  that  on  the  leeward 
side.  This  causes  a  building  up  of  pressure  within  the  building  and  a 
lesser  air  leakage  than  that  experienced  in  single  wa.ll  tests  as  determined 
in  the  laboratory.  It  is  assumed  that  actual  building  leakages  owing  to 
this  building  up  of  pressure  will  be  80  per  cent  of  laboratory  test  values. 
While  there  are  cases  where  this  is  not  true,  tests  in  actual  buildings 
substantiate  the  factor  for  the  general  case.  Tests  on  mechanically 
ventilated  classrooms  of  average  construction  have  shown  that  air 
infiltration  acts  quite  independently  of  the  planned  air  supply.  Accor- 
dingly, the  heating  or  cooling  load  owing  to  air  infiltration  from  natural 
causes  should  be  considered  in  addition  to  the  ventilating  load. 

The  air  exchange  owing  to  temperature  difference,  inside  to  outside,  is 
not  appreciable  in  low  buildings.  In  tall,  single  story  buildings  with 
openings  near  the  ground  level  and  near  the  ceiling,  this  loss  must  be 
considered.  Also  in  multi-story  buildings  it  is  a  large  item  unless  the 
sealing  between  various  floors  and  rooms  is  quite  perfect.  This  tempera- 
ture effect  is  a  chimney  action,  causing  air  to  enter  through  openings  at 
lower  levels  and  to  leave  at  higher  levels. 

A  complete  study  of  all  of  the  factors  involved  in  air  movement  through 
building  constructions  would  be  very  complex*  Some  of  the  complicating 

121 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

factors  are:  the  variations  in  wind  velocity  and  direction;  the  exposure  of 
the  building  with  respect  to  air  leakage  openings  and  with  ^ respect ^  to 
adjoining  buildings;  the  variations  in  outside  temperatures  asjnfluencing 
the  chimney  effect;  the  relative  area  and  resistance  of  openings  on  the 
windward  and  leeward  sides  and  on  the  lower  floors  and  on  the  upper 
floors;  the  influence  of  a  planned  air  supply  and  the  related  outlet  vents; 
and  the  variation  from  the  average  of  individual  building  units.  A  study 
of  infiltration  points  to  the  need  for  care  in  the  obtaining  of  good  building 
construction,  or  unnecessarily  large  heat  losses  will  result. 


INFILTRATION  THROUGH  WALLS 

Table  1  gives  data  on  infiltration  through  brick  and  frame  walls.  The 
brick  walls  listed  in  this  table  are  walls  which  show  poor  workmanship 
and  which  are  constructed  of  porous  brick  and  lime  mortar.  For  good 
workmanship,  the  leakage  through  hard  brick  walls  with  cement-lime 
mortar  does  not  exceed  one-third  the  values  given.  These  tests  indicate 
that  plastering  reduces  the  leakage  by  about  96  per  cent;  a  heavy  coat  of 
cold  water  paint,  50  per  cent;  and  3  coats  of  oil  paint  carefully  applied, 
28  per  cent.  The  infiltration  through  walls  ranges  from  6  to  25  per  cent 
of  that  through  windows  and  doors  in  a  10-story  office  building,  with 
imperfect  sealing  of  plaster  at  the  baseboards  of  the  rooms.  With  perfect 
sealing  the  range  is  from  0.5  to  2.7  per  cent  or  a  practically  negligible 
quantity,  which  indicates  the  importance  of  good  workmanship  in  proper 
sealing  at  the  baseboard.  It  will  be  noted  from  Table  1,  that  the  in- 
filtration through  properly  plastered  walls  can  be  neglected. 

The  value  of  building  paper  when  applied  between  sheathing  and 
shingles  is  indicated  by  Fig.  1,  which  represents  the  effect  on  outside 
construction  only,  without  lath  and  plaster.  The  effectiveness  of  plaster 
properly  applied  is  no  justification  for  the  use  of  low  grade  building  paper 
or  of  the  poor  construction  of  the  wall  containing  it.  Not  only  is  it 

TABLE  1.  INFILTRATION  THROUGH  WALLS** 

Expressed  in  cubic  feet  per  square  foot  per  hour 


TTPB  OF  WALL 

WIND  VKLOCITT,  MIUBS  EBB  HOUB 

5 

10 

15 

20 

25 

30 

8Ji  in.  Brick  TOL^gj-j- 

1.75 
0.017 

4.20 
0.037 

7.85 
0.066 

12.2 
0.107 

18.6 
0.161 

22.9 
0.236 

i  *>  •     T>—  j-t»  \\7  IT           /  i*ain.  _„„„_. 

1.44 
0.005 

3.92 
0.013 

7.48 
0.025 

11.6 
0.043 

16.3 
0.067 

21.2 
0.097 

13  in.  Bnck  Wall  1^^^^.. 

Frame  Wall,  with  lath  and  plaster^ 

0.03 

0.07 

0.13 

0.18 

0.23 

0.26 

_     »The  values  given  in  this  table  are  20  per  cent  less  than  test  values  to  allow  for  building  up  of  pressure 
in  rooms  and  are  based  on  test  data  reported  in  the  papers  listed  at  the  end  of  this  chapter. 

BeVd  *Ming  P8intcd  °f  Cedar  shingles'  sheathi*g.  building  paper,  wood  lath  and 


122 


CHAPTER  6.   AIR  LEAKAGE 


0.45 


0    20   40   60   80   100  120  140  160   180  200  220  240   260  280  300 
INFILTRATION,  C  FH  PER  SQ  FT  OF  WALL 

FIG.  1.   INFILTRATION  THROUGH  VARIOUS  TYPES  OF  SHINGLE  CONSTRUCTION 

difficult  to  secure  and  maintain  the  full  effectiveness  of  the  plaster  but 
also  it  is  highly  desirable  to  have  two  points  of  high  resistance  to  air  flow 
with  an  air  space  between  them. 

The  amount  of  infiltration  that  may  be  expected  through  simple  walls 
used  in  farm  and  other  shelter  buildings,  is  shown  in  Fig.  2.  The  infil- 
tration indicated  in  Figs.  1  and  2  is  that  determined  in  the  laboratory  and 
should  be  multiplied  by  the  factor  0.80  to  give  proper  working  values. 


<r  0.40  -  -  - 

g      ::: 


140      160      180     200     220 


INFILTRATION,  C  FH  PER  SQ  FT  OF  WALL 


FIG.  2.  INFILTRATION  THROUGH  SINGLE  SURFACE  WALLS  USED  IN  FARM  AND 
OTHER  SHELTER  BUILDINGS 

123 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


WINDOW  LEAKAGE 

The  amount  of  infiltration  for  various  types  of  windows  is  given  in 
Table  2.  The  fit  of  double-hung  wood  windows  is  determined  by  crack 
and  clearance  as  illustrated  in  Fig.  3.  The  length  of  the  perimeter  opening 
or  crack  for  a  double-hung  window  is  equal  to  three  times  the  width  plus 
two  times  the  height,  or  in  other  words,  it  is  the  outer  sash  ^  perimeter 
length  plus  the  meeting  rail  length.  Values  of  leakage  shown  in  Table  2 
for  the  average  double-hung  wood  window  were  determined  by  setting 
the  average  measured  crack  and  clearance  found  in  a  field  survey  of  a 
large  number  of  windows  on  nine  windows  tested  in  the  laboratory.  In 
addition,  the  table  gives  figures  for  a  poorly  fitted  window.  All  of  the 
figures  for  double-hung  wood  windows  are  for  the  unlocked  condition. 
Just  how  a  window  is  closed,  or  fits  when  it  is  closed,  has  considerable 
influence  on  the  leakage.  The  leakage  will  be  high  if  the  sash  are  short, 
if  the  meeting  rail  members  are  warped,  or  if  the  frame  and  sash  are  not 


FIG.  3.    DIAGRAM  ILLUSTRATING  CRACK  AND  CLEARANCE 

fitted  squarely  to  each  other.  It  is  possible  to  have  a  window  with 
approximately  the  average  crack  and  clearance  that  will  have  a  leakage 
at  least  double  that  of  the  figures  shown.  Values  for  the  average  double- 
hung  wood  window  in  Table  2  are  considered  to  be  easily  obtainable 
figures  provided  the  workmanship  on  the  window  is  good.  Should  it  be 
known  that  the  windows  under  consideration  are  poorly  fitted,  the  larger 
leakage  values  should  be  used.  Locking  a  window  generally  decreases  its 
leakage,  but  in  some  cases  may  push  the  meeting  rail  members  apart  and 
increase  the  leakage.  On  windows  with  large  clearances,  locking  will 
usually  reduce  the  leakage. 

Wood  casement  windows  may  be  assumed  to  have  the  same  unit 
leakage  as  for  the  average  double-hung  wood  window  when  properly 
fitted.  ^  Locking,  a  normal  operation  in  the  closing  of  this  type  of  window, 
maintains  the  crack  at  a  low  value. 

For  metal  pivoted  sash,  the  length  of  crack  is  the  total  perimeter  of  the 
movable  or  ventilating  sections.  Frame  leakage  on  steel  windows  may  be 
neglected  when  they  are  properly  grouted  with  cement  mortar  into  brick 
work  or  concrete.  When  they  are  not  properly  sealed,  the  linear  feet  of 
sash  section  in  contact  with  steel  work  at  mullions  should  be  figured  at 
25  per  cent  of  the  values  for  industrial  pivoted  windows  as  given  in 
Table  2. 

124 


CHAPTER  6.   AIR  LEAKAGE 


H  WINDOW.  IN.  OF  WATER 

D  p  H-  j- 

»  00  0  l\ 

{ 

y 

-A/ 

-E 

fl 

/< 

5U.U3 

45.69 

OZ 

•=> 
O 

40.89g 

CL 

a 

35,40s. 
28.90  g 

Q 

$ 
20.42 

0 

1 

I/ 

J 

y 

/ 

y 

/ 

i 

/ 

/ 

1 

i 

/ 

/  / 

l\ 

y 

/ 

/ 

\\ 

y 

\\ 

/ 

f/ 

1 

/ 

/ 

y 

I 

I 

A 

n 

i 

i 

7 

§ 

o.  04 

\ 

1 

/ 

A 
B 
C 

D 

-Without  storm  sash 
-Storm  sash,  suspend 
•Storm  sash,  fastened 
With  four  turn  button 
-Same  as  C  with  wool 
weatherstrip  applied 
to  storm  sash 

ed 
s 

1 

1 

// 

/ 

h 

j 

I 

/ 

1 

§ 

o 

U4 

*o-> 

7 

f 

I 

/ 

V 

) 

VJ 

/ 

X 

i 

o: 
CL. 

c 

/ 

f 

f 

M 

/ 

> 

'l 

50            100         150          200         250         300 
INFILTRATION,  CFH  PER  FOOT  OF  CRACK 

FIG.  4.    INFILTRATION  THROUGH  SASH  PERIMETER  OF  WINDOW  WITH  AND  WITHOUT 
STORM  SASH — J^-IN.  CRACK  AND  J^-IN.  CLEARANCE 

Leakage  values  for  storm  sash  are  given  in  Figs.  4  and  5.  When  storm 
sash  are  applied  to  well  fitted  windows,  very  little  reduction  in  infiltration 
is  secured,  but  the  application  of  the  sash  does  give  an  air  space  which 
reduces  the  heat  transmission  and  helps  prevent  the  frosting  of  the 
windows.  When  storm  sash  are  applied  to  poorly  fitted  windows,  a 
reduction  in  leakage  of  50  per  cent  may  be  secured. 


W,  IN.  OF  WATER 
:>»-•*- 

DO  K 

\    If 

y 

{ 

^  WIND  VELOCITY,  MILES  PER  HOUR 

1 

y 

- 

7 

li 

/ 

M 

/ 

/ 

/ 

^ 

/ 

( 

/ 

) 

/ 

z 
* 

f 

/ 

s 

] 

s 

jl 

/ 

/ 

fl 

^ 

PRESSURE  DROP  THROUG 

£  g  S 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

/ 

l\ 

\ 

/ 

* 

A-Without  storn 
B-  Storm  sash,  s 
C-  Storm  sash,  1 
with  four  tun 

isash 
uspend 
^stened 
i  button 

ed 

s 

/ 

/ 

/ 

/ 

/ 

s 

^ 

^ 

+ 

-? 

^ 

•*•• 

^ 

^ 

1 

La 

** 

ts 

E 

& 
0 

!• 

& 

I 

100          150          200          250         300         350          400         4 
1NF1LTRATION.C  F  H  PER  FOOT  OF  CRACK 

FIG.  5.    INFILTRATION  THROUGH  SASH  PERIMETER  OF  WINDOW  WITH  AND  WITHOUT 
STORM  SASH— H-m.  CRACK  AND  J^-IN.  CLEARANCE 

125 


HEATING   VENTIIIATING   AIR  CONDITIONING   GUIDE  1938 


TABLE  2,    INFILTRATION  THROUGH  WINDOWS 

Expressed  in  Cubic  Feet  per  Foot  of  Crack  per  Hour& 


Tr?«  OF  WINDOW 


REMARKS 


5 

10 

15 

20 

25 

30 

Double-Hung 
Wood  Sash 
Windows 
(Unlocked) 

1  Around  frame  in  masonry  wall  —  not  calkedb 

3.3 

8.2 

14.0 

20.2 

27.2 

34.6 

Around  frame  In  masonry  wall  —  calkedb  

0.5 

1.5 

2.6 

3.8 

4.8 

5.8 

Around  frame  in  wood  frame  construction^  

2.2 

6.2 

10.8 

16.6 

23.0 

30.3 

Total  for  average  window,  non-weather- 
stripped,  He-in.  crack  and  ?&-in.  clearancec. 
Includes  wood  frame  leakage^  

6.6 

21.4 

39.3 

59.3 

80.0 

103.7 

Ditto,  weatherstrippedd  

4.3 

15.5 

23.6 

35.5 

48.6 

63.4 

Total  for  poorly  fitted  window,  non-  weather- 
stripped,  5^-in.  crack  and  ?£-m.  clearance.* 
Includes  wood  frame  leakaged  „  

26.9 

69.0 

110.5 

153.9 

199.2 

249.4 

Ditto,  weatlierstrippedd  

5.9 

18.9 

34.1 

51.4 

70.5 

91.5 

Double-Hung 
Metal 
Windows* 

Non-weatierstripped,  locked  
Non-weatherstripped,  unlocked.  
Weatherstripped,  unlocked  

20 
20 
6 

45 
47 
19 

70 
74 
32 

96 
104 
46 

125 
137 
60 

154 

170 
76 

Rolled 
Section 
Steel 

Sash 
Windows^ 

Industrial  pivoteds,  J4-in.  crack.  
Architectural  projected,  J^-in.  crack**  
Architectural  projected,  %-in.  crackh  . 

52 
15 

20 
6 
14 

3 

8 

108 
36 
52 
18 
32 

10 
24 

176 
62 
88 
33 
52 

18 
38 

244 
86 
116 
47 
76 

26 
54 

304 
112 
152 
60 
100 

36 

72 

372 
139 
182 

74 
128 

48 
92 

Residential  casement,  l^-in.  crack*  

Residential  casement,  J^-in.  crack*  
Heavy  casement  section,  projected,  J^-in. 

cracki  .„      „ 

Heavy  casement  section,  projected  J^-in. 

•eraeki  

Hollow  Metal,  vertically  pivoted  windowf  

30 

88 

145 

186 

221 

242 

WIND  VELOCITY,  MILES  PIB  HOUR 


aThe  values  given  In  this  table  are  20  per  cent  less  than  test  values  to  allow  for  building  up  of  pressure  in 
rooms,  and  are  based  on  test  data  reported  in  the  papers  listed  at  the  end  of  this  chapter. 

f  fcThe  values  given  for  frame  leakage  are  per  foot  of  sash  perimeter  as  determined  for  double-hung  wood 
windows.  Some  of  the  frame  leakage  in  masonry  walls  originates  in  the  brick  wall  itself  and  cannot  be 
prevented  by  calking.  For  the  additional  reason  that  calking  is  not  done  perfectly  and  deteriorates  with 
tome,  it  is  considered  advisable  to  choose  the  masonry  frame  leakage  values  for  calked  frames  as  the  average 
determined  by  the  calked  and  not-calked  tests. 

cThe  fit  of  the  average  double-hung  wood  window  was  determined  as  }£-in.  crack  and  ?&-in.  clearance  by 
measurements  on  approximately  600  windows  under  heating  season  conditions. 

dThe  values  given  are  the  totals  for  the  window  opening  per  foot  of  sash  perimeter  and  include  frame 
leakage  and  so-called  elsewhere  leakage.  The  frame  leakage  values  included  are  for  wood  frame  construction 
but  apply  as  well  to  masonry  construction  assuming  a  50  per  cent  efficiency  of  frame  calking. 

•A  %-in.  crack  and  clearance  represents  a  poorly  fitted  window,  much  poorer  than  average. 

^Windows  tested  in  place  in  building. 

^Industrial  pivoted,  window  generally  used  in  industrial  buildings.  Ventilators  horizontally  pivoted 
at  center  or  slightly  above,  lower  part  swinging  out. 

_  ^Architectural  projected  made  of  same  sections  as  industrial  pivoted  except  that  outside  framing  member 
is  heavier,  and  refinements  in  weathering  and  hardware.  Used  in  semi-monumental  buildings  such  as 
schools.  Ventilators  swing  in  or  out  and  are  balanced  on  side  arms.  J^-in.  crack  is  obtainable  in  the  best 
practice  of  manufacture  and  installation,  Jfl-in.  crack  considered  to  represent  average  practice. 
•  Sf  •**  ^e  ^esi«n  and  section  shapes  as  so-called  heavy  section  casement  but  of  lighter  weight.  ki-£n.  crack 
practice*  m  P1"^^  <>f  manufacture  and  installation,  J^-in.  crack  considered  to  represent  average 


•  u+  -  -  ^i  "•—  ££.  se£tions-  Ventilators  swing  in  or  out  and  stay  set  at  any  degree  of  opening.  J^-in.  crack 
is  obtainable  m  the  best  practice  of  manufacture  and  installation,  fc-in.  crack  considered  to  represent 
average  practice. 

With  reasonable  care  in  installation  leakage  at  contacts  where  windows  are  attached  to  steel  frame- 
work and  at  muUions  is  negligible.  With  &-in.  crack,  representing  poor  installation,  leakage  at  contact 
Sndow?  i^thfSbk18  *  °ne"third'  and  at  mullions  about  one-sixth  of  that  given  for  industrial  pivoted 

126 


CHAPTER  6.   AIR  LEAKAGE 


DOO1  LEAKAGE 

Doors  vary  greatly  in  fit  because  of  their  "large  size  and  tendency  to 
warp.  For  a  well  fitted  door,  the  leakage  values  for  a  poorly  fitted  double- 
hung'wood  window  may  be  used.  If  poorly  fitted,  twice  this  figure  should 
be  used.  If  weatherstripped,  the  values  may  be  reduced  one-half.  A 
single  door  which  is  frequently  opened,  such  as  might  be  found  in  a  store, 
should  have  a  value  applied  which  is  three  times  that  for  a  well  fitted 
door.  This  extra  allowance  is  for  opening  and  closing  losses  and  is  kept 
from  being  greater  by  the  fact  that  doors  are  not  used  as  much  in  the 
coldest  and  windiest  weather. 

The  infiltration  rate  through  swinging  and  revolving  doors  is  generally 
a  matter  of  judgment  by  the  engineer  making  cooling  load  determinations 
and  in  the  absence  of  adequate  research  data  the  values  given  in  Table  3 
represent  current  engineering  practice.  These  values  are  based  on  the 
average  number  of  persons  in  a  room  at  a  specified  time,  which  may  also 
be  the  same  occupancy  assumed  for  determining  the  outside  ventilation 
requirements  outlined  in  Chapters  3  and  8. 

TABLE  3.    INFILTRATION  THROUGH  OUTSIDE  DOORS  FOR  COOLING  LOADS& 
Expressed  in  Cubic  Feet  per  Minute  per  Person  in  Room 


APPLICATION 

PA.IH  36  IN.  SWINGING 
DOOKS,  SINGLE 

ENTRANCEb 

"D^r-ilr                                                                       '                                      

7.5 
4.5 
7.0 
6.0 
25.0 
8.0 
2.5 
7.0 
2.5 
3.5 
5.0 
3.5 
3.0 
2.0 
2.5 
2.5 
3.5 

Tin?  tvne. 

Barber  Shop  

Drug  Store  -  

Furrier  

A/To.«'o  QVirvn                                                                                  -  •" 

Men  s  onop  

/"X-GC/N/i                                                                                         -  -  

Office  Building  

Public  Building  — 

Restaurant  -  

Ql-n-id  QfTvr*=-                                                                  *  *  —  — 

aFor  doors  located  m  omy  one  wa.u  <JL  wiicxc  v.^**,  ^  —  —  -  ---------  -  •„„:„„ 

Westibules  with  double  pair  swinging  doors,  infiltration  may  be  assumed  75  per  cent  of  swmgmg 

on  for  72  in.  revolving  doors  may  be  assumed  60  per  cent  of  swinging  door  values. 


SELECTION  OF  WIND  VELOCITY 

Although  all  authorities  do  not  agree  upon  the  value  of  the  wind  veloc- 
ity that  should  be  chosen  for  any  given  locality,  it  is  common  engineering 
practice  to  use  the  average  wind  velocity  during  the  three  coldest  months 
of  the  year.  Until  this  point  is  definitely  established  the  practice  of 
using  average  values  will  be  followed.  Average  wind  velocities  for  the 
monlhs  of  December,  January  and  February  for  various  cities  in  the 
United  States  and  Canada  are  given  in  Table  2,  Chapter  /. 


127 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

In  considering  both  the  transmission  and  infiltration  losses,  the  more 
exact  procedure  would  be  to  select  the  outside  temperature  and  the  wind 
velocity  corresponding  thereto,  based  on  Weather  Bureau  records,  which 
would  result  in  the  maximum  heat  demand.  Since  the  proportion  of 
transmission  and  infiltration  losses  varies  with  the  construction  and  is 
different  for  every  building,  the  proper  combination  of  temperature  and 
wind  velocity  to  be  selected  would  be  different  for  every  type  of  building, 
even  in  the  same  locality.  Furthermore,  such  a  procedure  would  necessi- 
tate a  laborious  cut-and-try  process  in  every  case  in  order  to  determine 
the  worst  combination  of  conditions  for  the  building  under  consideration. 
It  would  also  be  necessary  to  consider  heat  lag  due  to  heat  capacity  in  the 
case  of  heavy  masonry  walls,  and  other  factors,  to  arrive  at  the  most 
accurate  solution  of  the  problem.  Although  heat  capacity  should  be  con- 
sidered wherever  possible,  it  is  seldom  possible  to  accurately  determine  the 
worst  combination  of  outside  temperature  and  wind  velocity  for  a  given 
building  and  locality.  The  usual  procedure,  as  explained  in  Chapter  7, 
is  to  select  an  outside  temperature  which  is  not  more  than  15  F  above 
the  lowest  recorded,  and  the  average  wind  velocity  during  the  months 
of  December,  January  and  February. 

The  direction  of  prevailing  winds  may  usually  be  included  within  an 
angle  of  about  90  deg.  The  windows  that  are  to  be  figured  for  prevailing 
and  non-prevailing  winds  will  ordinarily  each  occupy  about  one-half  the 
perimeter  of  the  structure,  the  proportion  varying  to  a  considerable  extent 
with  the  plan  of  the  structure.  (See  discussion  of  wind  movement  in 
Chapter  36.) 

CRACK  LENGTH  USED  FOR  COMPUTATIONS 

In  no  case  should  the  amount  of  crack  used  for  computation  be  less 
than  half  of  the  total  crack  in  the  outside  walls  of  the  room.  Thus,  in  a 
room  with  one  exposed  wall,  take  all  the  crack;  with  two  exposed  walls, 
take  the  wall  having  the  most  crack;  and  with  three  or  four  exposed  walls, 
take  the  wall  having  the  most  crack;  but  in  no  case  take  less  than  half  the 
total  crack.  For  a  building  having  no  partitions,  whatever  wind  enters 
through  the  cracks  on  the  windward  side  must  leave  through  the  cracks 
on  the  leeward  side.  Therefore,  take  one-half  the  total  crack  for  com- 
puting each  side  and  end  of  the  building. 

The  amount  of  air  leakage  is  sometimes  roughly  estimated  by  assuming 
a  certain  number  of  air  changes  per  hour  for  each  room,  the  number  of 
changes  assumed  being  dependent  upon  the  type,  use  and  location  of  the 
room,  as  indicated  in  Table  4.  This  method  may  be  used  to  advantage  as 
a  check  on  the  calculations  made  in  the  more  exact  manner. 

MULTI-STORY  BUILDINGS 

In  tall  buildings,  infiltration  may  be  considerably  influenced  by  tem- 
perature difference  or  chimney  effect  which  will  operate  to  produce  a 
head  that  will  add  to  the  effect  of  the  wind  at  lower  levels  and  subtract 
from  it  at  higher  levels.  On  the  other  hand,  the  wind  velocity  at  lower 
levels  may  be  somewhat^  abated  by  surrounding  obstructions.  Further- 
more,^ the  chimney  effect  is  reduced  in  multi-story  buildings  by  the  partial 
isolation  of  floors  preventing  free  upward  movement,  so  that  wind  and 

128 


CHAPTER  6.   AIR  LEAKAGE 


TABLE  4.      AIR  CHANGES  TAKING  PLACE  UNDER  AVERAGE  CONDITIONS  EXCLUSIVE 
OF  AIR  PROVIDED  FOR  VENTILATION 


KIND  OP  ROOM  OB  BUILDING 


NUMBER  or  AIR  CHANGM 

TAKING  PLACE 

PER  Horn 


Rooms,  1  side  exposed I  1 

Rooms,  2  sides  exposed i  1J 

Rooms,  3  sides  exposed 2 

Rooms,  4  sides  exposed 2 

Rooms  with  no  windows  or  outside  doors._ 


Entrance  Halls — 
Reception  Halls 


2  to  3 
2 


Living  Rooms.—  ...........................................................................  i  1  to  2 


Dining  Rooms , 

Bath  Rooms 

Drug  Stores 

Clothing  Stores 

Churches,  Factories,  Lofts,  etc.. 


Ito2 

2 
2  to  3 

1 


temperature  difference  may  seldom  cooperate  to  the  fullest  extent. 
Making  the  rough  assumption  that  the  neutral  zone  is  located  at  mid- 
height  of  a  building,  and  that  the  temperature  difference  is  70  F,  the 
following  formulae  may  be  used  to  determine  an  equivalent  wind  velocity 
to  be  used  in  connection  with  Tables  1  and  2  that  will  allow  for  both  wind 
velocity  and  temperature  difference: 

-  1.75  a  (1) 


+  1.75  b  (2) 

where 

Mt  —  equivalent  wind  velocity  to  be  used  in  conjunction  with  Tables  1  and  2. 
j|f  =  wind  velocity  upon  which  infiltration  would  be  determined  if  tem- 
perature difference  were  disregarded. 
a  =  distance  of  windows  under  consideration  from  mid-height  of  building 

if  above  mid-height. 
b  —  distance  if  below  mid-height. 

The  coefficient  1.75  allows  for  about  one-half  the  temperature  difference  head. 

For  buildings  of  unusual  height,  Equation  1  would  indicate  negative 
infiltration  at  the  highest  stories,  which  condition  may,  at  times,  actually 
exist. 

Sealing  of  Vertical  Openings 

In  tall,  multi-story  buildings,  every  effort  should  be  made  to  seal  off 
vertical  openings  such  as  stair-wells  and  elevator  shafts  from  the  re- 
mainder of  the  building.  Stair-wells  should  be  equipped  with  self-closing 
doors,  and  in  exceptionally  high  buildings,  should  be  closed  off  into 
sections  of  not  over  10  floors  each.  Plaster  cracks  should  be  filled. 
Elevator  enclosures  should  be  tight  and  solid  doors  should  be  used. 

If  the  sealing  of  the  vertical  openings  is  made  effective,  no  allowance 
need  be  made  for  the  chimney  effect.  Instead,  the  greater^wind  move- 
ment at  the  high  altitudes  makes  it  advisable  to  install  additional  heating 
surface  on  the  upper  floors  above  the  level  of  neighboring  buildings,  this 
additional  surface  being  increased  as  the  height  is  increased.  One 

129 


HEATING   VENTILATING   Am  CONDITIONING   GUIDE  1938 

arbitrary  rule  is  to  increase  the  heating  surface  on  floors  above  neighboring 
buildings  by  an  amount  ranging  from  5  per  cent  to  20  per  cent.  This  extra 
heating  surface  is  required  only  on  the  windward  side  and^on  windy  days, 
and  hence  automatic  temperature  control  is  especially  desirable  with  such 
installations. 

In  stair-  wells  that  are  open  through  many  floor  levels  although  closed 
off  from  the  remainder  of  each  floor  by  doors  and  partitions,  the  strati- 
fication of  air  makes  it  advisable  to  increase  the  amount  of  heating  surface 
at  the  lower  levels  and  to  decrease  the  amount  at  higher  levels  even  to  the 
point  of  omitting  all  heating  surface  on  the  top  several  floor  levels.  One 
rule  is  to  calculate  the  heating  surface  of  the  entire  stair-well  in  the  usual 
way  and  to  place  50  per  cent  of  this  in  the  bottom  third,  the  normal 
amount  in  the  middle  third  and  the  balance  in  the  top  third. 

HEAT  EQUIVALENT  OF  AIR  INFILTRATION 
Sensible  Heat  Loss 

The  heat  required  to  warm  cold  outside  air,  which  enters  a  room  by 
infiltration,  to  the  temperature  of  the  room  is  given  by  the  equation: 

HB  =  0.24  Q  d  (ti  -  t0)  (3) 

where 

Hs  =  heat  required  to  raise  temperature  of  air  leaking  into  building  from  t0  to  t{ 

Btu  per  hour. 
0.24  =  specific  heat  of  air. 

Q  =  volume  of  outside  air  entering  building,  cubic  feet  per  hour. 
d  =  density  of  air  at  temperature  t0,  pounds  per  cubic  foot. 
t\  —  room  air  temperature,  degrees  Fahrenheit. 
t0  ~  outside  air  temperature,  degrees  Fahrenheit. 

Latent  Heat  Loss 

When  it  is  intended  to  add  moisture  to  air  leaking  into  a  room  for  the 
maintenance  of  proper  winter  comfort  conditions,  it  is  necessary  to 
determine  the  heat  equivalent  to  evaporate  the  required  amount  of  water 
vapor,  which  may  be  calculated  by  the  equation  : 


7000 
where 

Hi  =  heat  required  to  increase  moisture  content  of  air  leaking  into  building  from 
Mo  to  Mi,  Btu  per  hour. 

Q  —  volume  of  outside  air  entering  building,  cubic  feet  per  hour. 

d  =  density  of  air  at  temperature  ti,  pounds  per  cubic  foot. 
Mi  —  vapor  density  of  inside  air,  grains  per  pound  of  dry  air. 
Mo  =  vapor  density  of  outside  air,  grains  per  pound  of  dry  air. 

L  =  latent  heat  of  vapor  at  MI,  Btu  per  pound. 

It  is  sufficiently  accurate  to  use  d  =  0.075  Ib,  in  which  case  equation  3 
reduces  to  5  and  if  the  latent  heat  of  vapor  is  assumed  for  general  condi- 
tions as  1060  Btu  per  pound  equation  4  reduces  to  6. 

Hs  =  0.018  Q  (ti  -  to)  (5) 

fli  =  0.0114  Q  (Mi  -  Mo)  (6) 

While  a  heating  reserve  must  be  provided  to  warm  inleaking  air  on 
the  windward  side  of  a  building,  this  does  not  necessarily  mean  that  the 

130 


CHAPTER  6.   AIR  LEAKAGE 


heating  plant  must  be  provided  with  a  reserve  capacity,  since  the  inleaking 
air,  warmed  at  once  by  adequate  heating  surface  in  exposed  rooms,  will 
move  transversely  and  upwardly  through  the  building,  thus  relieving 
other  radiators  of  a^part  of  their  load.  The  actual  loss  of  heat  of  a  building 
caused  by  infiltration  is  not  to  be  confused  with  the  necessity  for  pro- 
viding additional  heating  capacity  for  a  given  space.  Infiltration  is  a 
disturbing  factor  in  the  heating  of  a  building,  and  its  maximum  effect 
(maximum  in  the  sense  of  an  average  of  wind  velocity  peaks  during  the 
heating  season  above  some  reasonably  chosen  minimum)must  be  met 
by  a  properly  distributed  reserve  of  heating  capacity,  which  reserve,  how- 
ever, is  not  in  use  at  all  places  at  the  same  time,  nor  in  any  one  place  at 

all  times.  

REFERENCES 

Air  Leakage,  by  F.  C.  Houghten  and  C.  C.  Schrader  (A.S.H.V.E.  TRANSACTIONS, 
Vol.  30,  1924,  p.  105). 

Air  Leakage  around  Window  Openings,  by  C.  C.  Schrader  (A.S.H.V.E.  TRANSACTIONS, 
Vol.  30,  1924,  p.  313). 

Neutral  Zone  in  Ventilating,  by  J.  E.  Emswiler  (A.S.H.V.E.  TRANSACTIONS,  Vol.  32, 
1926,  p.  59). 

Infiltration  through  Plastered  and  Unplastered  Brick  Walls,  by  F.  C.  Houghten  and 
Margaret  Ingels  (A.S.H.V.E.  TRANSACTIONS,  Vol.  33,  1927,  p.  377). 

Effect  of  Frame  Calking  and  Storm  Sash  on  Infiltration  around  and  through  Windows, 
by  W.  M.  Richtmann  and  C.  Braatz  (A.S.H.V.E.  TRANSACTIONS,  Vol.  34,  1928T  p.  547). 

Air  Leakage  on  Metal  Windows  in  a  Modern  Office  Building,  by  F.  C.  Houghten  and 
M.  E.  O'Connell  (A.S.H.V.E.  TRANSACTIONS,  Vol.  34,  1928,  p.  321). 

The  Weathertightness  of  Rolled  Section  Steel  Windows,  by  J.  E.  Emswiler  and 
W.  C.  Randall  (A.S.H.V.E.  TRANSACTIONS,  Vol.  34,  1928,  p.  527). 

Air  Leakage  through  a  Pivoted  Metal  Window,  by  F.  C.  Houghten  and  M.  E. 
O'Connell  (A.S.H.V.E.  TRANSACTIONS,  Vol.  34,  1928,  p.  519). 

Air  Infiltration  through  Various  Types  of  Brick  Wall  Construction,  by  G.  L.  Larson, 
D.  W.  Nelson  and  C.  Braatz  (A.S.H.V.E.  TRANSACTIONS,  Vol.  35, 1929,  p.  183). 

Pressure  Differences  across  Windows  in  Relation  to  W:ind  Velocity,  by  J.  E.  Emswiler 
and  W.  C.  Randall  (A.S.H.V.E.  TRANSACTIONS,  Vol.  36,  1930,  p.  83). 

Air  Infiltration  Through  Various  Types  of  Wood  Frame  Construction,  by  G.  L. 
Larson,  D.  W.  Nelson  and  C.  Braatz  (A.S.H.V.E.  TRANSACTIONS,  Vol.  36,  1930,  p.  99). 

Air  Infiltration  Through  Double-Hung  Wood  Windows,  by  G.  L.  Larson,  D.  W. 
Nelson  and  R.  W.  Kubasta  (A.S.H.V.E.  TRANSACTIONS,  Vol.  37,  1931,  p.  571). 

Flue  Action  in  Tall  Buildings,  by  H.  L.  Alt  (Heating,  Piping  and  Air  Conditioning, 
May,  1932). 

Air  Infiltration  Through  Steel  Framed  Windows,  by  D.  0.  Rusk,  V.  H.  Cherry  and 
L.  Boelter  (Heating,  Piping  and  Air  Conditioning,  October,  1932). 

Investigation  of  Air  Outlets  in  Class  Room  Ventilation,  by  G.  L.  Larson,  D.  W. 
Nelson  and  R.  W.  Kubasta  (A.S.H.V.E.  TRANSACTIONS,  Vol.  38,  1932,  p.  463). 

Influence  of  Stack  Effect  on  the  Heat  Loss  in  Tall  Buildings,  by  Axel  Marin  (A.S.H. 
V.E.  TRANSACTIONS,  Vol.  40,  1934,  p.  377). 

Wind  Velocities  Near  a  Building  and  Their  Effect  on  Heat  Loss,  by  F.  C.  Houghten, 
J.  L.  Blackshaw,  and  Carl  Gutberlet  (A.S.H.V.E.  TRANSACTIONS,  Vol.  40,  1934,  p.  387). 

Fuel  Saving  Resulting  from  the  Use  of  Storm  Windows  and  Doors,  by  A.  P.  Kratz  and 
S.  Konzo  (A.S.H.V.E.  TRANSACTIONS,  Vol.  42,  1936,  p.  87). 

The  Infiltration  Problem  of  Multiple  Entrances,  by  A.  M.  Simpson  and  K.  B.  Atkinson 
(A.S.H.V.E.  JOURNAL  SECTION,  Heating,  Piping  and  Air  Conditioning,  June,  1936). 

Infiltration  Characteristics  of  Entrance  Doors,  by  A.  M.  Simpson  (Refrigerating 
Engineering,  June,  1936). 

Heating  Requirements  of  an  Office  Building  as  Influenced  by  the  Stack  Effect,  by 
F.  C.  Houghten  and  Carl  Gutberlet  (A.S.H.V.E.  JOURNAL  SECTION,  Heating,  Piping 
and  Air  Conditioning,  July,  1937). 

131 


HEATING   VENTILATING   AIR  CONDITIONING    GUIDE  1938 

PROBLEMS  IN  PRACTICE 

1  •  What  two  natural  forces  cause  infiltration? 

c.  Wind  causes^  pressure  to  be  exerted  on  one  or  two  sides  of  a  building  with  consequent 
movement  of  air  through  openings. 

i>.  Temperature  difference  inside  to  outside  causes  a  difference  in  density  with  con- 
sequent entrance  of  air  at  lower  openings  and  exit  of  air  at  higher  openings. 

2  •  What  is  the  neutral  zone  as  applied  to  infiltration  in  buildings? 

Due  to  temperature  difference  inside  air  tends  to  flow  out  of  openings  near  the  top  of 
the  building  and  is  replaced  by  outside  air  coming  in  at  lower  openings.  At  some  height 
no  flow  occurs  in  or  out.  This  is  referred  to  as  the  neutral  zone  and  often  is  taken  at  the 
mid-height  of  the  building  but  may  be  higher  or  lower  than  this  depending  on  several 
factors. 

3  •  In  what  type  of  structure  is  infiltration  due  to  temperature  difference 
of  importance? 

In  tall  open  buildings,  in  multi-story  buildings  inadequately  sealed  between  floors  and 
in  stair- wells  for  multi-story  buildings  the  temperature  difference  effect  is  important. 

4  •  What  procedure  is  sometimes  used  to  compensate  for  this  temperature 
or  chimney  effect  in  stair-wells? 

One  rulejs  to  place  50  percent  of  the  calculated  radiation  in  the  bottom  third,  the  normal 
amount  in  the  middle  third  and  the  remainder  in  the  top  third. 

5  •  Why  is  it  customary  to  apply  a  correction  factor  to  laboratory  values  before 
calculating  infiltration  in  buildings? 

Most,  if  not  all,  laboratory  values  have  been  determined  by  exerting  a  certain  wind 
pressure  across  a  single  thickness  of  building  construction.  In  actual  building  con- 
struction the  pressure  drop  due  to  wind  velocity  takes  place  in  two  steps,  one  through 
the  windward  and  the  other  through  the  leeward  wall.  Tests  indicate  that  the  leakage 
in  actual  construction  will  be  about  80  per  cent  of  laboratory  values  and  therefore  this 
factor  has  been  applied  in  making  up  the  tables  in  this  chapter.  The  curves  represent 
laboratory  data  as  taken  with  no  correction  applied. 

6  •  Is  infiltration  through  walls  of  importance? 

In  the  case  of  compound  walls  of  good  construction  the  heat  loss  due  to  infiltration  is 
usually  negligibly  low.  In  the  case  of  single  thickness  walls  without  building  paper 
properly  applied,  the  heat  loss  due  to  air  leakage  may  be  very  high. 

7  •  How  are  the  wind  velocities  and  outside  temperatures  selected  for  infil- 
tration calculations  in  heating? 

It  is  common  practice  to  take  the  average  wind  velocity  for  the  three  coldest  months 
and  the  temperature  as  15  F  above  the  coldest  recorded  by  the  Weather  Bureau  during 
the  proceeding  10  years. 

80  Show  the  probable  combined  effects  of  infiltration  due  to  temperature 
difference  and  wind  velocity  on  the  ground  floor  and  on  the  15th  floor  of  a  20- 
story  building  200  ft  high  with  a  12  mph  wind  blowing. 

At  the  ground  floor  the  effective  velocity  is  increased  to: 


Ke  =  V122  +  1.75  X  100  =  17.8  mph 
At  the  15th  floor  level  it  would  be  reduced  to: 

Me  =  V122  -  1.75  X  50  =  7.5  mph 
9  •  What  is  the  value  of  storm  sash  in  reducing  infiltration? 

The  reduction  depends  on  the  relative  fit  of  the  window  and  the  storm  sash.  Fig.  4 
indicates  for  storm  sash  buttoned  on  a  reduction  at  20  mph  from  about  52  cfh  per  foot 
of  crack  to  42  cfh.  Fig.  5  indicates  a  reduction  for  a  storm  sash  buttoned  over  a  loosely 
fitted  window  from  185  to  90  cfh. 

132 


Chapter  7 

HEATING  LOAD 

Heat  Demand  Design  Factors,  Method  of  Procedure,  Inside 
and  Outside  Temperatures,  Wind  Velocity  Effects,  Auxiliary 
Heat  Sources,  Wall  Condensation,  Heat  Loss  Computation 

TO  design  any  system  of  heating,  the  maximum  probable  heat^demand 
must  be  accurately  estimated  in  order  that  the  apparatus  installed 
shall  be  capable  of  maintaining  the  desired  temperature  at  all  times.    The 
factors  which  govern  this  maximum  heat  demand — most  of  which  are 
seldom,  if  ever,  in  equilibrium — include  the  following: 

1.  Outside  temperature.  1 

2.  Rain  or  snow.  Outside  Conditions 

3.  Sunshine  or  cloudiness.  (The  Weather) 

4.  Wind  velocity.  J 


5.  Heat  transmission  of  exposed  parts  of  building. 

6.  Infiltration  of  air  through  cracks,  crevices  and 

open  doors  and  windows. 

7.  Heat  capacity  of  materials. 

8.  Rate  of  absorption  of  solar  radiation  by  exposed 

materials. 

9.  Inside  temperatures. 

10.  Stratification  of  air. 

11.  Type  of  heating  system. 

12.  Ventilation  requirements. 

13.  Period  and  nature  of^  occupancy. 

14.  Temperature  regulation. 


Building 
Construction 


Inside 
Conditions 


The  inside  conditions  vary  from  time  to  time,  the  physical  properties  of 
the  building  construction  may  change  with  age,  and  the  outside  conditions 
are  changing  constantly.  Just  what  the  worst  combination  of  all  of  these 
variable  factors  is  likely  to  be  in  any  particular  case  is. therefore  con- 
iectural.  Because  of  the  nature  of  the  problem,  extreme  precision  in 
estimating  heat  losses  at  any  time,  while  desirable,  is  hard  of  attainment. 

The  procedure  to  be  followed  in  determining  the  heat  loss  from  any 
building  can  be  divided  into  seven  consecutive  steps,  as  follows: 

1.  Determine  on  the  inside  air  temperature,  at  the  breathing  line  or  the i  30-in.  line, 
which  is  to  be  maintained  in  the  building  during  the  coldest  weather.  (See  Table  1.)  ^ 

2.  Determine  on  an  outside  air  temperature  for  design  purposes,  t^0  WfP1?1^; 
temperatures  recorded  in  the  locality  in  question,  which  will  provide  for  all  but  the 
most  severe  weather  conditions.   Such  conditions  as  may  exist  for  only  a  few .consecu- 
tive hours  are  readily  taken  care  of  by  the  heat  capacity  of  the   building  itself. 


(See  Table  2.) 

133 


HEATING  VENTILATING  AIR  CONDITIONING   GUIDE  1938 


3.  Select  or  compute  the  heat  transmission  coefficients  for  outside  walls  and  glass; 
also  for  inside  walls,  floors,  or  top-floor  ceilings,  if  these  are  next  to  unheated  space; 
include  roof  if  next  to  heated  space.   (See  Chapter  5.) 

4.  Measure  up  net  outside  wall,  glass  and  roof  next  to  heated  spaces,  as  well  as  any 
cold  walls,  floors  or  ceilings  next  to  unheated  space.  Such  measurements  are  made  from 
building  plans,  or  from  tie  actual  building. 

5.  Compute  the  heat  transmission  losses  for  each  kind  of  wall,  glass,  floor,  ceiling 
and  roof  in  the  building  by  multiplying  the  heat  transmission  coefficient  in  each  case 
by  the  area  of  the  surface  in  square  feet  and  the  temperature  difference  between  the 
inside  and  outside  air.    (See  Items  1  and  2.) 

6.  Select  unit  values  and  compute  the  heat  equivalent  of  the  infiltration  of  cold  air 
taking  place  around  outside  doors  and  windows.  These  unit  values  depend  on  the  kind  or 
width  of  crack  and  wind  velocity,  and  when  multiplied  by  the  length  of  crack  and  the 
temperature  difference  between  the  inside  and  outside  air,  the  result  expresses  the  heat 
required  to  warm  up  the  cold  air  leaking  into  the  building  per  hour.   (See  Chapter  6.) 

7.  The  sum  of  the  heat  losses  by  transmission  (Item  5)  through  the  outside  wall  and 
glass,  as  well  as  through  any  cold  floors,  ceilings  or  roof,  plus  the  heat  equivalent  (Item  6) 
of  the  cold  air  entering  by  infiltration  represents  the  total  heat  loss  equivalent  for  any 
building. 

Item  7  represents  the  heat  losses  after  the  building  is  heated  and  under 
stable  operating  conditions  in  coldest  weather.  Additional  heat  is 
required  for  raising  the  temperature  of  the  air,  the  building  materials  and 
the  material  contents  of  the  building  to  the  specified  standard  inside 
temperature. 

The  rate  at  which  this  additional  heat  is  required  depends  upon  the 
heat  capacity  of  the  structure  and  its  material  contents  and  upon  the 
time  in  which  these  are  to  be  heated. 

This  additional  heat  may  be  figured  and  allowed  for  as  conditions  re- 


TABLE  1.   WINTER  INSIDE  DRY-BULB  TEMPERATURES  USUALLY  SPECIFIED* 


TTFB  07  BUILDING 

DwjFAHR 

TYPH  OP  BUILDING 

DB&FAHE 

SCHOOLS 
Class  rooms  

70-72 

THEATERS  — 
Seating  space 

68-72 

Assembly  rooms.  .. 

68-72 

Lounge  rooms. 

68-72 

Gymnasiums  

55-65 

Toilets 

68 

Toilets  and  baths  

70 

Wardrobe  and  locker  rooms  
Kitchens.-             .„ 

65-68 
66 

HOTELS  — 
Bedrooms  and  baths 

70 

Dining  and  lunch  rooms.    

65-70 

Dining  rooms 

70 

Playrooms. 

60-65 

Kitchens  and  laundries 

fifi 

Natatoriums.  .   « 

75 

Ballrooms 

65-68 

HOSPITALS— 
Private  rooms.  

70-72 

Toilets  and  service  rooms.  

FTOMES  

68 
70-72 

Private  rooms  (surgical)  

70-80 

STORES.-.  _  

65-68 

Operating  rooms  .      ,   . 

70-95 

PUBLIC  BUILDINGS 

68-72 

Wards  

68 

WARM  AIR  BATHS 

I2fi 

Kitchens  and  laundries. 

66 

STEAM  BATHS 

110 

Toiler 

68 

FACTORIES  AND  MACHINE  SHOPS 

fin  ft*? 

Bathrooms-. 

70-80 

H  OUNDRIES  AND  BOILER  SHOPS 

Kfkftn 

PAINT  SHOPS...        

80 

**•  ^S«m08tT?>mf<i?ablef  <5r'bulb  temperature  to  be  maintained  depends  on  the  relative  humidity  and 
£  Chapter  3          ^"^          "  conaidered  together  constitute  what  is  termed  the  effective  temperature. 


134 


CHAPTER  7.  HEATING  LOAD 


quire,  but  inasmuch  as  the  heating  system  proportioned  for  taking  care 
of  the  heat  losses  will  usually  have,  a  capacity  about  100  per  cent  greater 
than  that  required  for  average  winter  weather,  and  inasmuch  as  most 
buildings  may  either  be  continuously  heated  or  have  more  time  allowed 
for  heating-up  during  the  few  minimum  temperature  days,  no  allowance 
is  made  except  in  the  size  of  boilers  or  furnaces. 

INSIDE  TEMPERATURES 

The  inside  air  temperature  which  must  be  maintained  within  a  building 
and  which  should  always  be  stated  in  the  heating  specifications  is  under- 
stood to  be  the  dry-bulb  temperature  at  the  breathing  line,  5  ft  above  the 
floor,  or  the  30-in.  line,  and  not  less  than  3  ft  from  the  outside*  walls. 
Inside  air  temperatures,  usually  specified,  vary  in  accordance  with  the  use 
to  which  the  building  is  to  be  put  and  Table  1  presents  values  which  con- 
form with  good  practice. 

The  proper  dry-bulb  temperature  to  be  maintained  depends  upon  the 
relative  humidity  and  air  motion,  as  explained  in  Chapter  3.  In  other 
words,  a  person  may  feel  warm  or  cool  at  the  same  dry-bulb  temperature, 
depending  on  the  relative  humidity  and  air  motion.  The  optimum  winter 
effective  temperature  for  sedentary  persons,  as  determined  at  the  A.S.H. 
V.E.  Research  Laboratory,  is  66  deg.1 

According  to  Fig.  6,  Chapter  3,  for  so-called  still  air  conditions,  a 
relative  humidity  of  approximately  50  per  cent  is  required  to  produce  an 
effective  temperature  of  66  deg  when  the  dry-bulb  temperature  is  70  F. 
However,  even  where  provision  is  made  for  artificial  humidification,  the 
relative  humidity  is  seldom  maintained  higher  than  40  per  cent  during  the 
extremely  cold  weather,  and  where  no  provision  is  made  for  humidifica- 
tion, the  relative  humidity  may  be  20  per  cent  or  less.  Consequently,  in 
using  the  figures  listed  in  Table  1,  consideration  should  be  given  to 
whether  provision  is  to  be  made  for  humidification,  and  if  so,  the  actual 
relative  humidity  to  be  maintained. 

Temperature  at  Proper  Level:  In  making  the  actual  heat-loss  compu- 
tations, however,  for  the  various  rooms  in  a  building  it  is  often  necessary 
to  modify  the  temperatures  given  in  Table  1  so  that  the  air  temperature 
at  the  proper  level  will  be  used.  By  air  temperature  at  the  proper  level  is 
meant,  in  the  case  of  walls,  the  air  temperature  at  the  mean  height  be- 
tween floor  and  ceiling;  in  the  case  of  glass,  the  air  temperature  at  the 
mean  height  of  the  glass;  in  the  case  of  roof  or  ceiling,  the  air  temperature 
at  the  mean  height  of  the  roof  or  ceiling  above  the  floor  of  the  heated 
room ;  and  in  the  case  of  floors,  the  air  temperature  at  the  floor  level.  In 
the  case  of  heated  spaces  adjacent  to  unheated  spaces,  it  will  usually  be 
sufficient  to  assume  the  temperature  in  such  spaces  as  the  mean  between 
the  temperature  of  the  inside  heated  spaces  and  the  outside  air  tempera- 
ture, excepting  where  the  combined  heat  transmission  coefficient  of  the 
roof  and  ceiling  can  be  used,  in  which  case  the  usual  inside  and  outside 
temperatures  should  be  applied.  (See  discussion  regarding  the  use  of 
combined  coefficients  of  pitched  roofs,  unheated  attics  and  top-floor 
ceilings  Chapter  5.) 


*See  Chapter  3,  p.  63. 

135 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

High  Ceilings:  Research  data  concerning  stratification  of  air  in  build- 
ings are  lacking,  but  in  general  it  may  be  said  that  where  the  increase  in 
temperature  is  due  to  the  natural  tendency  of  jthe  warmer  or  less  dense 
air  to  rise,  as  where  a  direct  radiation  system  is  installed,  the  temperature 
of  the  air  at  the  ceiling  increases  with  the  ceiling  height.  The  relation, 
however,  is  not  a  straight-line  function,  as  the  amount  of  increase  per  foot 
of  height  apparently  decreases  as  the  height  of  the  ceiling  increases,  ac- 
cording to  present  available  information2. 

Where  ceiling  heights  are  under  20  ft,  it  is  common  engineering  practice 
to  consider  that  the  Fahrenheit  temperature  increases  2  per  cent  for  each 
foot  of  height  above  the  breathing  line.  This  rule,  sufficiently  accurate 
for  most  cases,  will  give  the  probable  air  temperature  at  any  given  level 
for  a  room  heated  by  direct  radiation.  Thus,  the  probable  temperature 
in  a  room  at  a  point  3  ft  above  the  breathing  line,  if  the  breathing  line 
temperature  is  70  F,  will  be 

(1.00  +  3  X  .02)  70  =  74.2  F. 

With  certain  types  of  heating  and  ventilating  systems,  which  tend  to 
oppose  the  natural  tendency  of  warm  air  to  rise,  the  temperature  differ- 
ential between  floor  and  ceiling  can  be  greatly  reduced.  These  include 
unit  heaters,  fan-furnace  heaters,  and  the  various  types  of  mechanical 
ventilating  systems.  The  amount  of  reduction  is  problematical  in  certain 
instances,  as  it  depends  upon  many  factors  such  as  location  of  heaters, 
air  temperature,  and  direction  and  velocity  of  air  discharge.  In  some 
cases  it  has  been  possible  to  reduce  the  temperature  between  the  floor 
and  ceiling  by  a  few  degrees,  whereas,  in  other  cases,  the  temperature  at 
the  ceiling  has  actually  been  increased  because  of  improper  design,  instal- 
lation or  operation  of  equipment.  So  much  depends  upon  the  factors 
enumerated  that  it  is  not  advisable  to  allow  less  than  1  per  cent  per  foot 
(and  usually  more)  above  the  breathing  line  in  arriving  at  the  air  tem- 
perature at  any  given  level  for  any  of  these  types  of  heating  and  ventilating 
systems,  unless  the  manufacturers  are  willing  to  guarantee  that  the  par- 
ticular type  of  equipment  under  consideration  will  maintain  a  smaller 
temperature  differential  for  the  specific  conditions  involved. 

Temperature  at  Floor  Level:  In  determining  mean  air  temperatures 
just  above  floors  which  are  next  to  ground  or  unheated  spaces,  a  tempera- 
ture 5  deg  lower  than  the  breathing-line  temperature  may  be  used,  pro- 
vided the  breathing-line  temperature  is  not  less  than  55  F. 

OUTSIDE  TEMPERATURES 

The  outside  temperature  used  in  computing  the  heat  loss  from  a  build- 
ing is  seldom  taken  as  the  lowest  temperature  ever  recorded  in  a  given 
locality.  Such  temperatures  are  usually  of  short  duration  and  are  rarely 
repeated  in  successive  years.  It  is  therefore  evident  that  a  temperature 
somewhat  higher  than  the  lowest  on  record  may  be  properly  assumed  in 
making  the  heat-loss  computations. 


3Temperature  Gradient  Observations  in  a  Large  Heated  Space,  by  G.  L.  Larson,  D.  W.  Nelson  and 
O.  C.  Cromer  (A.S.H.V.E.  TRANSACTIONS,  Vol.  39,  1933,  p.  243). 

Tests  of  Three  Heating  Systems  in  an  Industrial  Type  of  Building,  by  G.  L.  Larson,  D.  W.  Nelson  and 
John  James  (A.S.H.V.E.  TRANSACTIONS,  Vol.  41,  1935,  p.  185). 

136 


CHAPTER  7.   HEATING  LOAD 


The  outside  temperature  to  be  assumed  in  the  design  of  any  heating 
system  is  ordinarily  not  more  than  15  deg  above  the  lowest  recorded  tem- 
perature as  reported  by  the  Weather  Bureau  during  the  preceding  10 
years  for  the  locality  in  which  the  heating  system  is  to  be  installed.  In 
the  case  of  massive  and^well  insulated  buildings  in  localities  where  the 
minimum  does  not  prevail  for  more  than  a  few  hours,  or  where  the  lowest 
recorded  temperature  is  extremely  unusual,  more  than  15  deg  above  the 
minimum  may  be  allowed,  due  primarily  to  the  fly-wheel  effect  of  the  heat 
capacity  of  the  structure.  The  outside  temperature  assumed  and  used  in 
the  design  should  always  be  stated  in  the  heating  specifications.  Table  2 
lists  the  coldest  dry-bulb  temperatures  ever  recorded  by  the  Weather 
Bureau  at  the  places  listed. 

If  Weather  Bureau  reports  are  not  available  for  the  locality  in  question, 
then  the  reports  for  the  station  nearest  to  this  locality  are  to  be  used, 
unless  some  other  temperature  is  specifically  stated  in  the  specifications. 
In  computing  the  average  heat  transmission  losses  for  the  heating  season 
in  the  United  States  the  average  outside  temperature  from  October  1 
to  May  1  should  be  used. 

WIND  VELOCITY  EFFECTS 

The  effect  of  wind  on  the  heating  requirements,  of  any  building  should 
be  given  consideration  under  two  heads: 

1.  Wind  movement  increases  the  heat  transmission  of  walls,  glass,  and  roof,  affecting 
poor  walls  to  a  much  greater  extent  than  good  walls. 

2.  Wind  movement  materially  increases  the  infiltration  (inleakage)  of  cold  air  through 
the  cracks  around  doors  and  windows,  and  even  through  the  building  materials  them- 
selves, if  such  materials  are  at  all  porous. 

Theoretically  as  a  basis  for  design,  the  most  unfavorable  combination 
of  temperature  and  wind  velocity  should  be  chosen.  It  is  entirely  possible 
that  a  building  might  require  more  heat  on  a  windy  day  with  a  moderately 
low  outside  temperature  than  on  a  quiet  day  with  a  much  lower  outside 
temperature.  However,  the  combination  of  wind  and  temperature  which 
is  the  worst  would  differ  with  different  buildings,  because  wind  velocity 
has  a  greater  effect  on  buildings  which  have  relatively  high  infiltration 
losses.  It  would  be  possible  to  work  out  the  heating  load  for  a^  building 
for  several  different  combinations  of  temperature  and  wind  velocity  which 
records  show  to  have  occurred  and  to  select  the  worst  combination;  but 
designers  generally  do  not  feel  that  such  a  degree  of  refinement  is  justified. 
Therefore,  pending  further  studies  of  actual  buildings,  it  is  recommended 
that  the  average  wind  movement  in  any  locality  during  December, 
January  and  February  be  provided  for  in  computing  (1)  the  heat  trans- 
mission of  a  building,  and  (2)  the  heat  required  to  take  care  of  the  infiltra- 
tion of  outside  air. 

The  first  condition  is  readily  taken  care  of,  as  explained  in  Chapter  5, 
by  using  a  surface  coefficient /0  for  the  outside  wall  surface  which  is  based 
on  the  proper  wind  velocity.  In  case  specific  data  are  lacking  for  any 
given  locality,  it  is  sufficiently  accurate  to  use  an  average  wind  velocity  of 
approximately  15  mph  which  is  the  velocity  upon  which  the  heat  trans- 
mission coefficient  tables  in  Chapter  5  are  based. 

In  a  similar  manner,  the  heat  allowance  for  infiltration  through  cracks 

137 


HEATING  VENTILATING  AIR  CONDITIONING   GUIDE  1938 


TABLE  2.    CLIMATIC  CONDITIONS  COMPILED  FROM  WEATHER  BUREAU  RECORDS** 


COL.  A 

COL.  B 

COL.C 

COL.  D 

COL.  E 

COL.F 

State 

City 

Average 
Temp., 
Oct.  1st- 
May  1st 

Lowest 
Tempera- 
ture 
Ever 
Reported 

Average 
Wind  Vel- 
ocity Dec., 
Jan.,  Feb., 
Miles  per 
Hour 

Direction 
of  Prevail- 
ing Wind, 
Dec.,  Jan., 
Feb. 

Ala..  

Mobile  

58.9 

-1 

10.4 

N 

Birmingham  

53.8 

-10 

8.5 

N 

Ariz  

Phoenix.  — 

59.5 

12 

6.4 

E 

Flagstaff.  

35.8 

-25 

7.8 

SW 

Ark  __ 

Fort  Smith  

50.4 

-15 

8.1 

E 

Little  Rock  

51.6 

-12 

8.7 

NW 

Calif 

San  Francisco  

54.2 

27 

7.6 

N 

Los  Angeles  

58.5 

28 

6.3 

NE 

Colo  

Denver  

38.9 

-29 

7.5 

S 

Grand  Junction  

38.9 

-21 

5.3 

NW 

Conn. 

New  Haven  

38.4 

-15 

9.7 

N 

D.  C. 

Washington 

43.4 

-15 

7.1 

NW 

Fla  

Jacksonville  

62.0 

10 

9.2 

NE 

Ga  

Atlanta  

51.5 

-8 

12.1 

NW 

Savannah  

58.5 

8 

9.5 

NW 

Idaho  

Lewiston  

42.3 

-23 

5.3 

E 

Pocatello  

35.7 

-28 

9.6 

SE 

111  

Chicago  

36.4 

-23 

12.5 

W 

Springfield  

39.8 

-24 

10.1 

NW 

Ind  

Indianapolis.  
Evansville  

40.3 
45.1 

-25 
-16 

11.5 
9.8 

SW 
S 

Iowa  

Dubuque...  

33.9 

-32 

7.1 

NW 

Sioux  City  

32.6 

-35' 

11.6 

NW 

Kans  

Concordia  

39.8 

-25 

8.1 

S 

Ky. 

Dodge  City  
Louisville  

41.4 
45.3 

-26 
-20 

9.8 
9.9 

NW 
SW 

La  

New  Orleans  

61.6 

7 

8.8 

N 

Shreveport  

56.2 

-5 

8.9 

SE 

Me  

Eastport.  

31.5 

-23 

12.0 

W 

Portland  

33.8 

-21 

9.2 

NW 

Md  

Baltimore.  

43.8 

-7 

7.8 

NW 

Mass.  

Boston.  

38.1 

-18 

11.2 

W 

Mich  

Alpena 

29.6 

—28 

12  4 

W 

Detroit  

35.8 

-24 

12.7 

SW 

Marquette  

28.3 

-27 

11.1 

NW 

Minn  

Duluth 

24  3 

—41 

12.6 

SW 

Minneapolis.  

29.4 

-33 

n!s 

NW 

Miss  

Vicksburg.  

56.8 

-1 

8.3 

SE 

Mo  

St.  Joseph  
St.  Louis  

40.7 
43.6 

-24 
-22 

9.3> 
11.6 

NW 
S 

Mont  

Springfield  

44.3 
34.0 

-29 
-49 

10.8 

SE 
W 

Havre  

27.6 

-57 

~o 

SW 

Nebr  

Lincoln  

37.0 

-29 

10.5 

S 

North  Platte  

35.4 

-35 

8.5 

W 

Nev  „.. 

Tonopah.  

39.4 

-10 

10.0 

SE 

Winnemucca  

37.9 

-28 

8.7 

NE 

N.  H.  .. 

Concord  

33.3 

-35 

6.6 

NW 

N.  T. 

N.Y.:::::::::: 

Atlantic  City  
Albany  

41.6 
35.2 

-9 
-24 

15.9 
8.1 

NW 
S 

Buffalo  

34.8 

-20 

17.2 

W 

New  York  

40.7 

-14 

17.1 

NW 

^United  States  data  from  U.  S.  Weather  Bureau. 
Canadian  data  from  Meteorological  Service  of  Canada. 

138 


CHAPTER  7.   HEATING  LOAD 


TABLE  2.    CLIMATIC  CONDITIONS  COMPILED  FROM  WEATHER  BUREAU  RECORDS* 

(Continued) 


COL.  A 

COL.B 

COL.  C 

COL.  D 

CouE 

CoL,F 

State 
or 
Province 

City 

Average 
Temp., 
Oct.  1st- 
May  1st 

Lowest 
Tempera- 
ture Ever 
Reported 

Average 
Wind  Vel- 
ocity Dec., 
Jan.,  Feb., 
Miles  per 
Hour 

Direction 
of  Prevail- 
ing Wind, 
Dec.,  Jan., 
Feb. 

N.  M  
N.  C  

N.  Dak  
Ohio 

Santa  Fe.  
Raleigh.-.  
Wilmington  
Bismarck  
Devils  Lake  
Cleveland 

38.3 
50.0 
54.2 
24.6 
20.3 
37  2 

-13 
-2 
5 
-45 
-44 
—  17 

7.8 
8.2 
8.5 
9.1 
10.6 
13  0 

NE 
SW 

sw 

NW 
W 

sw 

Okla  
Oreg  

Pa  

R  I 

Columbus  
Oklahoma  City  
Baker  
Portland  
Philadelphia  
Pittsburgh  
Providence.  

39.9 
47.9 
35.2 
46.1 
42.7 
41.0 
37.2 

-20 
-17 
-24 
-2 
-6 
-20 
-17 

12,0 
12.0 
6.9 
7.5 

11.0 
11.7 
12.8 

sw 

N 
SE 

S 

NW 
W 
NW 

s.  c  

Charleston  

57.4 

7 

10.6 

SW 

S  Dak. 

Columbia  
Huron  

54.0 
28.2 

-2 
-43 

8.1 
10.6 

NE 
NW 

Tenn  

Rapid  City.  
Knoxville  
Memphis  

33.4 
47.9 
51.1 

-34 
-16 
-9 

8.2 
7.8 
9.7 

W 
SW 

s 

Texas  
Utah  

El  Paso  
Fort  Worth  
San  Antonio  
Modena..  

Salt  Lake  City  

53.5 
55.2 
60.6 
36.3 
40.0 

-5 
-8 
4 
-24 
-20 

10.4 
10.4 
8.0 
8.8 
6.7 

NW 
NW 
NE 
W 
SE 

Vt  
Va  

Wash  

W.  Va. 

Burlington  
Norfolk.  
Lynchburg.  
Richmond  
Seattle  
Spokane  
Elkins  

31.5 
49.3 
46.8 
47.0 
44.8 
37.7 
39.4 

-29 
2 
-7 
-3 
3 
-30 
-28 

11.8 
12.5 
7.1 
7.9 
11.3 
7.1 
6.6 

S 
N 
NW 
SW 
SE 
SW 
W 

Wis  

Parkersburg.™  
Green  Bay  

42.6 
30.0 

-27 
-36 

7.5 
10.4 

SW 

SW 

Wyo.  

Alta. 
B.  C  

La  Crosse~  
Milwaukee..  

Lander  
Edmonton  

Victoria 

31.7 
33.4 
30.7 
30.0 
23.0 
43.9 

-43 
-25 
-41 
-40 
-57 
-  1.5 

7.3 
11.5 
6.0 
5.0 
6.5 
12.5 

s 

W 

NW 
SW 

sw 

N 

Man  

N  B 

Vancouver  
Winnipeg  

Fredericton 

42.0 
17.5 
27.0 

2 

-47 
35 

4.5 
10.0 
9.6 

E 

NW 
NW 

N.  S  
Ont. 

Yarmouth  

London 

35.0 
32.6 

-12 
-27 

14.2 
10.3 

NW 
SW 

Ottawa  
Port  Arthur  

Toronto 

26.5 
22.4 
32.9 

-34 
-37 
-26.5 

8.4 
7.8 
13.0 

NW 
NW 
SW 

P.  E.  I  
Que  

Charlottetown  
Montreal  

29.0 

27.8 

-27 
-29 

9.4 
14.3 

sw 
sw 

Sask.._  
Yukon  

Quebec  
Prince  Albert  
Dawson  

24.2 
15.8 
2.1 

-34 
-70 
-68 

13.6 
5.1 
3.7 

sw 

W 

s 

^United  States  data  from  U.  S.  Weather  Bureau. 
Canadian  data  from  Meteorological  Service  of  Canada. 

139 


HEATING  VENTIUITING   AIR  CONDITIONING  GUIDE  1938 

and  walls  (Tables  1  and  2,  Chapter  6)  must  be  based  on  the  proper  wind 
velocity  for  a  given  locality.  In  the  case  of  tall  buildings  special  attention 
must  be  given  to  infiltration  factors.  (See  Chapter  6). 

In  the  past  many  designers  have  used  empirical  exposure  factors  which 
were  arbitrarily  chosen  to  increase  the  calculated  heat  loss  on  the  side  or 
sides  of  the  building  exposed  to  the  prevailing  winds.  It  is  also  possible 
to  differentiate  among  the  various  exposures  more  accurately  by  calcu- 
lating the  infiltration  and  transmission  losses  separately  for  the  different 
sides  of  the  building,  using  different  assumed  wind  velocities.  Recent 
investigations  show,  however,  that  the  wind  direction  indicated  by 
Weather  Bureau  instruments  does  not  always  correspond  with  the 
direction  of  actual  impact  on  the  building  walls,  due  to  deflection  by 
surrounding  buildings. 

The  exposure  factor,  which  is  still  in  use  by  many  engineers,  is  usually 
taken  as  15  per  cent,  and  is  added  to  the  calculated  heat  loss  on  the  side  or 
sides  exposed  to  what  is  considered  the  prevailing  winter  wind.  There  is  a 
need  for  actual  test  data  on  this  point,  and  pending  the  time  when  it  can 
be  secured,  the  question  must  be  left  to  the  judgment  of  the  designing 
engineer.  It  should  be  remembered  that  the  values  of  U  in  the  tables  in 
Chapter  5  are  based  on  a  wind  velocity  of  15  mph  and  that  the  infiltration 
figures  are  supposed  to  be  selected  from  the  tables  in  Chapter  6  to  cor- 
respond to  the  wind  velocities  given  in  Table  2  of  the  present  chapter. 

The  Heating,  Piping  and  Air  Conditioning  Contractors  National  Associ- 
ation has  devised  a  method8  for  calculating  the  square  feet  of  equivalent 
direct  radiation  required  in  a  building.  This  method  makes  use  of  ex- 
posure factors  which  vary  according  to  the  geographical  location  and  the 
angular  situation  of  the  construction  in  question  in  reference  to  pre- 
vailing winds  and  the  velocity  of  them. 

AUXILIARY  HEAT  SOURCES 

The  heat  supplied  by  persons,  lights,  motors  and  machinery  should 
always  be  ascertained  in  the  case  of  theaters,  assembly  halls,  and  in- 
dustrial plants,  but  allowances  for  such  heat  sources  must  be  made  only 
after  careful  consideration  of  all  local  conditions.  In  many  cases,  these 
heat  sources  should  not  be  allowed  to  affect  the  size  of  the  installation  at 
all,  although  they  may  have  a  marked  effect  on  the  operation  and  con- 
trol of  the  system.  In  general,  it  is  safe  to  say  that  where  audiences  are 
involved,  the  heating  installation  must  have  sufficient  capacity  to  bring 
the  building  up  to  the  stipulated  inside  temperature  before  the  audience 
arrives.  In  industrial  plants,  quite  a  different  condition  exists,  and  heat 
sources,  if  they  are  always  available  during  the  period  of  human  occu- 
pancy, may  be  substituted  for  a  portion  of  the  heating  installation.  In 
no  case  should  the  actual  heating  installation  (exclusive  of  heat  sources) 
be  reduced  below  that  required  to  maintain  at  least  40  F  in  the  building. 

Electric  Motors  and  Machinery 

Motors  and  the  machinery  which  they  drive,  if  both  are  located  in  the 
room,  convert  all  of  the  electrical  energy  supplied  into  heat,  which  is 


•See  Standards  of  Heating,  Piping  and  Air  Conditioning  Contractors  National  Association. 

140 


CHAPTER  7.  HEATING  LOAD 


retained  in  the  room  if  the  product  being  manufactured  is  not  removed 
until  its  temperature  is  the  same  as  the  room  temperature. 

If  power  is  transmitted  to  the  machinery  from  the  outside,  then  only 
the  heat  equivalent  of  the  brake  horsepower  supplied  is  used.  In  the 

first  case  the  Btu  supplied  per  hour  =  Motor  horsepower  and 

Efficiency  of  motor 

in  the  second  case  Btu  per  hour  =  bhp  X  2546,  in  which  2546  is  the 
Btu  equivalent  of  1  hp-hour.  In  high-powered  mills  this  is  the  chief 
source  of  heating  and  it  is  frequently  sufficient  to  overheat  the  building 
even  in  zero  weather,  thus  requiring  cooling  by  ventilation  the  year 
round. 

The  heat  (in  Btu  per  hour)  from  electric  lamps  is  obtained  by  multi- 
plying the  watts  per  lamp  by  the  number  of  lamps  and  by  3.415.  One 
cubic  foot  of  producer  gas  gives  off  about  150  Btu  per  hour;  one  cubic 
foot  of  illuminating  gas  gives  off  about  535  Btu  per  hour;  and  one  cubic 
foot  of  natural  gas  gives  off  about  1000  Btu  per  hour.  A  Welsbach 
burner  averages  3  cu  ft  of  gas  per  hour  and  a  fish-tail  burner,  5  cu  ft 
per  hour.  For  information  concerning  the  heat  supplied  by  persons, 
see  Chapter  3. 

In  intermittently  heated  buildings,  besides  the  capacity  necessary 
to  care  for  the  normal  heat  loss  which  may  be  calculated  according  to 
customary  rules,  additional  capacity  should  be  provided  to  supply  the 
heat  necessary  to  warm  up  the  cold  material  of  the  interior  walls,  floors, 
and  furnishings.  Tests  have  shown  that  when  a  cold  building  has  had  its 
temperature  raised  to  about  60  F  from  an  initial  condition  of  about  0  F, 
the  heat  absorbed  from  the  air  by  the  material  in  the  structure  may  vary 
from  50  per  cent  to  150  per  cent  of  the  normal  heat  loss  of  the  building. 
It  is  therefore  necessary,  in  order  to  heat  up  a  cold  building  within  a 
reasonable  length  of  time,  to  provide  such  additional  capacity.  If  the 
interior  material  is  cold  when  people  enter  a  building,  the  radiation  of 
heat  from  the  occupants  to  the  cold  material  will  be  greater  than  is 
normal  and  discomfort  will  result.  (See  Chapter  3.) 

WALL  CONDENSATION 

Condensation  in  the  interior  surfaces4  of  buildings  may  cause  irrep- 
arable damage  to  manufactured  articles  and  machinery.  It  often  results 
in  short-circuiting  of  electric  power,  and  causes  disintegration  of  roof 
structures  not  properly  protected. 

The  prevalence  of  moisture  on  a  surface  is  caused  by  the  contact  of 
the  warm  humid  air  in  a  building  with  surfaces  below  the  dew-point 
temperature.  It  can  be  eliminated  by  (1)  raising  the  surface  temperature 
with  increased  air  velocities  passing  over  the  surface,  or  adding  a  sufficient 
thickness  of  insulation,  and  (2)  by  lowering  the  humidity  which  is  often 
not  possible  due  to  manufacturing  processes. 

The  condensation  of  moisture  within  walls5  is  an  important  problem 
with  may  types  of  construction  under  adverse  conditions.  The  tempera- 

*Preventing  Condensation  on  Interior  Building  Surfaces,  by  Paul  D.  Close  (A.S.H.V.E.  TRANSACTIONS, 
Vol.  36,  1930,  p.  153). 

"Condensation  within  Walls,  by  F.  B.  Rowley,  A.  B.  Algren  and  C.  E.  Lund  (A.S.H.V.E.  JOURNAL 
SECTION,  Healing,  Piping  and  Air  Conditioning,  January,  1938). 

141 


HEATING   VENTIIATING  AIR  CONDITIONING   GUIDE  1938 

tures  of  the  various  parts  of  a  wall  are  controlled  by  the  type  and  amount 
of  insulation  used  and  the  vapor  densities  in  the  corresponding  sections 
are  controlled  by  the  type  of  vapor  barriers  installed.  The  transmission 
of  heat  and  vapor  through  a  wall  should  be  considered  together,  and  in 
most  cases  the  proper  combination  of  insulation  and  vapor  barriers  will 
eliminate  the  possibilities  of  condensation  within  walls.  A  consideration 
often  overlooked  in  problems  of  condensation  within  walls  is  that  a  vapor 
barrier  should  be  placed  on  the  warm  side  and  not  on  the  cold  side  of 
a  wall. 

HEAT  LOSS  COMPUTATION  EXAMPLE 


Buift-up  Cooftoq  on  3*  Coocr«Ve  Hoof  Deck 


5fe  U   UnqAwfcnol  Ax*  MorHi  *  S 

#e—  1 

net      1  —  IS  Window*  «od» 
l.f       r   »de  4'JfUuLt. 
fcron   1 
nor     i*           5*St&neConcra£e0n 
faec-fn-p      3-Ond«rCooc«t« 
j'£         OR  Dirt  -7 

•outh 

Lenqlb  ttrf-0* 

\ 

S 

O 

I 

r 

orCra 
Solid  V 

&~ 

xxlDoow 

-BP 

5 

FIG.  1.   ELEVATION  OF  FACTORY  BUILDING 


Philadelphia,  Pa. 

-6F 


..Northwest 
60  F 


1.  LOCATION 

2.  LOWEST  OUTSIDE  TEMPERATURE.    (Table  2) 

3.  BASE  TEMPERATURE:  In  this  example  a  design  temperature  10  F  above  lowest 

on  record  instead  of  15  F  is  used.    Hence  the  base  temperature  — 

(-  6  +  10)  =  +  4  F. 

4.  DIRECTION  OF  PREVAILING  WIND  (during  Dec.,  Jan.,  Feb.) 

5.  BREATHING-LINE  TEMPERATURE  (5  ft  from  floor) 

6.  INSIDE  AIR  TEMPERATURE  AT  ROOF: 

The  air  temperature  just  below  roof  is  higher  than  at  the  breathing  line. 
Height  of  roof  is  16  ft,  or  it  is  16  —  5  «  11  ft  above  breathing  line.  Allowing 
2  per  cent  per  foot  above  5  ft,  or  2  X  11  —  22  per  cent,  makes  the  tem- 
perature of  the  air  under  the  roof  =  1,22  X  60  =  73.2  F. 

7.  INSIDE  TEMPERATURE  AT  WALLS: 

The  air  temperature  at  the  mean  height  of  the  walls  is  greater  than  at 
the  breathing  fine.  The  mean  height  of  the  walls  is  8  ft  and  allowing  2  per 
cent  per  foot  above  5  ft,  the  average  mean  temperature  of  the  walls  is 
1.06  X  60  =  63.6  F.  By  similar  assumptions  and  calculations,  the  mean 
temperature  of  the  glass  will  be  found  to  be  64.2  F  and  that  of  the  doors 
61.2  F. 


8.  AVERAGE  WIND  VELOCITY  (Table  2) 

9.  OVER-ALL  DIMENSIONS  (See  Fig.  1)... 
10.  CONSTRUCTION: 


..11.0  mph 


120  x  50  x  16  ft 


Walls — 12-in.  brick,  with  %-in.  plaster  applied  directly  to  inside  surface. 
Roof — 3-in.  stone  concrete  and  built-up  roofing. 

142 


CHAPTER  7.   HEATING  LOAD 


Floor — 5-in.  stone  concrete  on  3-in.  cinder  concrete  on  dirt. 

Doors— One  12  ft  x  12  ft  wood  door  (2  in.  thick)  at  each  end. 

Windows — Fifteen,  9  ft  x  4  ft  single  glass  double-hung  windows  on  each  side. 

11.  TRANSMISSION  COEFFICIENTS: 

Walls—  (Table  3,  Chapter  5,  Wall  2B) U  =  0.34 

Roof—  (Table  11,  Chapter  5,  Roofs  2A  and  3A) U  =  0.77 

Floor—  (Table  10,  Chapter  5,  Floors  5A  and  6A) U  =  0.63 

Doors— -(Table  13B,  Chapter  5) U  =  0.46 

Windows— (Table  13A,  Chapters) U  -  1.13 

12.  INFILTRATION  COEFFICIENTS: 

Windows— Average  windows,  non-weatherstripped,  Ke-in-  crack  and 
5^4-in.  clearance.  The  leakage  per  foot  of  crack  for  an  11-mile  wind 
velocity  is  25.0  cfh.  (Determined  by  interpolation  of  Table  2, 
Chapter  6.)  The  heat  equivalent  per  hour  per  degree  per  foot  of 
crack  is  taken  from  Chapter  6. 

25.0  X  0.018  =  0.45  Btu  per  deg  Fahrenheit  per  foot  of  crack. 

Doors — Assume  infiltration  loss  through  door  crack  twice  that  of  windows 
or  2  X  0.45  =  0.90  Btu  per  deg  Fahrenheit  per  foot  of  crack. 

Walls— As  shown  by  Table  1,  Chapter  6,  a  plastered  wall  allows  so  little 
infiltration  that  in  this  problem  it  may  be  neglected. 

13.  CALCULATIONS:    See  calculation  sheet,  Table  3. 


TABLE  3. 


CALCULATION  SHEET  SHOWING  METHOD  OF  ESTIMATING  HEAT  LOSSES  OF 
BUILDING  SHOWN  IN  FIG.  1 


PART  OF  BUILDING 

WIDTH 

IN 

FEET 

HEIGHT 

IN 

FEET 

NET  SUR- 
FACE AREA 
OR  CRACK 
LENGTH 

COEFFI- 

CIENT 

TEMP. 
DIFF. 

TOTAL 
BTU 

North  Wall: 
Pn>k,  M-1"^  piaster      ,      ., 

60 
12 

Ipair 

16 
12 
doors 

656 
144 
60 

0.34 
0.46 
0.90 

59.6 
57.2 
57.2 

13,293 
3,789 
1,544* 

Poors  (2-ii?T  wood)  , 

Min-  ^rac.k      -.  ' 

West  Wall: 

Ttriclc,  J^-in  .  pfastfr      

120 
15x4 
Double 
Windov 

16 
9 
Hung 
re  (15) 

1380 
540 

450 

0.34 
1.13 

0.45 

59.6 
60.2 

60.2 

27,964 
36,734 

6,095a 

niass  (Siiigte)L_ 

^  in  Cr?»cV  ....         ~  ,   - 

South  Wall 

Same  as  North  Wall 

18,626 

TCaat  Ws^l                 ,            

Same  as  West  Wall 

70,793 

Roof,  3-in.  concrete  and  slag- 
surfaced  built-up  roofing  

50 

120 

6000 

0.77 

69.2 

319,704 

Floor,  5-in.  stone  concrete  on 
3-in.  cinder  concrete.^_..____ 

50 

120 

6000 

0.63 

5b 

18,900 

GRAND  TOTAL  of  heat  required  for  building  in  Btu  pet 

honr           ,-,-                         L       _^  1L 

517.442 

aThis  building  has  no  partitions  and  whatever  air  enters  through  the  cracks  on  the  windward  side  must 
leave  through  the  cracks  on  the  leeward  side.  Therefore,  only  one-half  of  the  total  crack  will  be  used  in 
computing  infiltration  for  each  side  and  each  end  of  building. 

bA  5  F  temperature  differential  is  commonly  assumed  to  exist  between  the  air  on  one  side  of  a  large 
floor  laid  on  the  ground  and  the  ground. 


143 


HEATING   VENTILATING  Am  CONDITIONING  GUIDE  1938 


PROBLEMS  IN  PRACTICE 

1  •  What  is  the  relation  between  the  sensible  heat  loss  from  a  building  and  the 
heat  required  for  humidification? 

A  house  with  a  volume  of  14,000  cu  ft  has  a  heat  loss  120  Mbh  for  standard  uninsulated 
frame  construction  and  a  70  F  temperature  difference.  Assuming  a  leakage  rate  of 
1J^  air  changes  per  hour  it  would  require  about  10  Mbh  to  maintain  a  relative  humidity 
of  45  per  cent  when  the  outside  air  is  0  F  and  50  per  cent  relative  humidity.  By  using 
an  insulation  such  as  rock  wool,  the  sensible  heat  loss  of  this  house  may  be  reduced  to 
approximately  77  Mbh.  The  insulation  does  not  affect  the  humidification  load,  which 
now  assumes  greater  importance. 

2  •  What  inside  dry-bulb  temperatures  are  usually  assumed  for:   (a)  homes, 
(b)  schools,  (c)  public  buildings? 

Referring  to  Table  1: 

a.  70  to  72  F. 

b.  Temperature  varies  from  55  to  75  F,  depending  on  the  room.  Classrooms,  for  instance, 
are  usually  specified  as  70  to  72  F. 

c.  68  to  72  F. 

3  •  How  is  the  outside  temperature  selected  for  use  hi  computing  heat  losses? 

The  outside  temperature  used  in  computing  heat  losses  is  generally  taken  from  10  to  15  F 
higher  than  the  lowest  recorded  temperature  as  reported  by  the  Weather  Bureau  during 
the  preceding  10  years  for  the  locality  in  which  the  heating  system  is  to  be  installed. 
In  some  cases  where  the  lowest  recorded  temperature  is  extremely  unusual,  the  design 
temperature  is  taken  even  higher  than  15  F  above  the  lowest  recorded  temperature. 

4  •  What  are  the  effects  of  wind  movement  on  the  heating  load? 

a.  Wind  movement  increases  the  heat  transmission  of  walls,  glass,  and  roof;  it  affects 
poor  walls  to  a  much  greater  extent  than  good  walls. 

b.  Wind  movement  materially  increases  the  infiltration  (inleakage)  of  cold  air  through 
the  cracks  around  doors  and  windows,  and  even  through  the  building  materials  them- 
selves if  such  materials  are  at  all  porous. 

5  •  Calculate  the  heat  given  off  by  eighteen  200-watt  lamps. 

200  X  18  X  3.415  -  12,294  Btu  per  hour. 

6  •  A  two-story,  six-room,  frame  house,  28-ft  by  30-ft  foundation,  has  the 
following  proportions : 

Area  of  outside  walls,  1992  sq  ft. 

Area  of  glass,  333  sq  ft. 

Area  of  outside  doors,  54  sq  ft. 

Cracks  around  windows,  440  ft. 

Cracks  around  doors,  54  ft. 

Area  of  second  floor  ceiling,  783  sq  ft. 

Volume,  first  and  second  floors,  13,010  cu  ft. 

Ceilings,  9  ft  high. 

The  minimum  temperature  for  the  heating  season  is  —  34  F,  and  the  required 
inside  temperature  at  the  30-in.  level  is  70  F.  The  average  number  of  degree 
days  for  a  heating  season  is  7851,  and  the  average  wind  velocity  is  10  mph, 
northwest.  * 


The  walls  are  constructed  of  2-m.  by  4-in.  studs  with  wood  sheathing,  building 
paper,  and  wood  siding  on  the  outside,  and  wood  lath  and  plaster  on  the  inside. 
Windows  are  single  glass,  double-hung,  wood,  without  weatherstrips.  The 
second  floor  ceiling  is  metal  lath  and  plaster,  without  an  attic  floor.  The  roof 
is  of  wood  shingles  on  wood  strips  with  rafters  exposed.  The  area  of  the  roof  is 
20  per  cent  greater  than  the  area  of  the  ceiling.  Select  values  for  the  following : 
(a)  U  for  walls;  (b)  U  for  glass;  (c)  U  for  second  floor  ceiling;  (d)  U  for  roof; 


144 


CHAPTER  7.   HEATING  LOAD 


(e)  U  for  ceiling  and  roof  combined;  (f)  air  leakage,  cubic  feet  per  hour  per  foot 
of  window  crack;  (g)  air  leakage,  cubic  feet  per  hour  per  foot  of  door  crack. 

a.  0.25  (Table  5,  Chapter  5). 

b.  1.13  (Table  13,  Chapter  5). 

c.  0.69  (Table  8,  Chapter  5). 

d.  0.46  (Table  12,  Chapter  5). 

e.  0.31  (Equation  6,  Chapter  5). 
/.  21.4  (Table  2,  Chapter  6). 

g.  42.8,  which  is  double  the  window  leakage. 

7  •  Using  the  data  of  Question  6,  calculate  the  maximum  Btu  loss  per  hour  for 
the  various  constructions,  and  show  the  percentage  of  the  total  heat  which  is 
lost  through  each  construction  described. 

Assume  2  per  cent  rise  in  temperature  for  each  foot  in  height.  The  average  temperature 
will  be  72.8  F  for  walls,  doors,  and  windows,  and  79.1  F  for  the  second  floor  ceiling. 


a.  Outside  walls 

b.  Glass 

c.  Doors 

d.  Second  floor  ceiling 

e.  Air  leakage,  windows 
/.  Air  leakage,  doors 

Total 


46,200  Btu  loss 
34,950  Btu  loss 

5,670  Btu  loss 
24,050  Btu  loss 
15,750  Btu  loss 

3,865  Btu  loss 


35.4  per  cent  of  total 
26.7  per  cent  of  total 

4.4  per  cent  of  total 
18.4  per  cent  of  total 
12.1  per  cent  of  total 

3.0  per  cent  of  total 


130,485  Btu  loss  100.0  per  cent  of  total 

8  •  For  the  house  in  Question  6,  place  1-in.  insulation  in  the  outside  walls  and 
second  floor  ceiling;  k  for  insulation  =  0.34.    Use  weatherstrip  on  doors  and 
windows,  and  double  glass  on  the  windows;  G  =  0.55.     Calculate  or  select  the 
following  values:  (a)  U  for  walls;  (b)  U  for  glass;  (c)  U  for  second  floor  ceiling; 
(d)  U  for  combination  of  ceiling  and  roof;  (e)  air  leakage,  cubic  feet  per  hour 
per  foot  of  door  crack;  (f)  air  leakage,  cubic  feet  per  hour  per  foot  of  window 
crack. 

a.  0.144 

b.  0.55 

c.  0.23 

d.  0.16 

e.  15.5 
/.  31.0 

9  •  Calculate  the  maximum  Btu  loss  per  hour  and  show  the  percentage  loss  by 
each  channel  for  the  house  as  insulated  in  Question  8. 


a.  Outside  walls 

b.  Glass 

c.  Doors 

d.  Ceiling 

e.  Air  leakage,  windows 
/.  Air  leakage,  doors 

Total 


26,650  Btu  loss 
17,000  Btu  loss 

5,670  Btu  loss 
12,420  Btu  loss 
11,400  Btu  loss 

2,795  Btu  loss 


35.1  per  cent  of  total 
22.4  per  cent  of  total 

7.4  per  cent  of  total 
16.4  per  cent  of  total 
15.1  per  cent  of  total 

3.6  per  cent  of  total 


75,935  Btu  loss       100.0  per  cent  of  total 


10  •  From  the  results  of  Questions  7  and  9,  calculate  the  Btu  saved  and  the 
percentage  saved  by  each  change  in  construction. 


UNINSULATED 

INB^™ 

BTU  SAVED 

Fra  CENT  SATED 

a.  Outside  walls  
b.  Glass  
c.  Doors  
d.  Ceiling  

46,200 
34,950 
5,670 
24,050 
15,750 
3,865 

26,650 
17,000 
5,670 
12,420 
11,400 
2,795 

19,550 
17,950 
0 
11,630 
4,350 
1,070 

42.3 
51.4 
0 
48.3 
27.6 
27.7 

f.  Air  leakage,  windows 

/.  Air  leakage,  doors.  

145 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 

11  •  From  the  results  of  Questions  7  and  9,  calculate  the  heat  loads  per  heating 
season  in  Btu  and  note  the  savings  by  better  construction. 

The  7851  degree  days  for  the  heating  season  multiplied  by  24  hours,  times  the  Btu  loss 
per  hour  for  1  F  drop  in  temperature  gives  the  Btu  load  per  heating  season. 

Saving  -  262,000,000  -  152,500,000  =  109,500,000  Btu. 

12  •  The  dry-bulb  temperature  and  the  relative  humidity  at  the  ceiling  of  a 
mixing  room  in  a  bakery  are  80  F  and  60  per  cent,  respectively.    The  roof  is  a 
4-in.  concrete  deck  covered  with  built-up  roofing.    If  the  lowest  outside  tem- 
perature to  be  expected  is  —  10  F,  what  thickness  of  rigid  fiber  insulation  will  be 
required  to  prevent  condensation? 

From  Table  11,  Chapter  5,  U  for  the  uninsulated  roof  =  0.72.  From  Table  2,  Chapter  5, 
k  for  rigid  fiber  insulation  =  0.33.  From  the  psychrometric  chart  the  dew-point  of  air 
at  80  F  and  60  per  cent  relative  humidity  is  65  F.  The  ceiling  temperature,  therefore, 
must  not  drop  below  65  F  if  condensation  is  to  be  prevented. 

When  equilibrium  is  established,  the  amount  of  heat  flowing  through  any  component 
part  of  a  construction  is  the  same  for  each  square  foot  of  area. 

Therefore, 

U  [80  -  (-10)  ]  =  1.65  (80  -  65) 
where 

U  is  the  transmittance  of  the  insulated  roof. 
Solving  the  equation,  U  =  0.275. 

The  resistance  of  the  insulated  roof  =    ~  0_,    =  3.64. 


The  resistance  of  the  uninsulated  roof  =   77-^7  —  1.39. 

U.7J 

The  resistance  of  the  insulation  =  3.64  —  1.39  =  2.25. 

Resistance  per  inch  of  insulation  =  n  Q0    =  3.0. 

U.oo 

Since  a  resistance  of  2.25  is  required,  and  1  in.  of  insulation  has  a  resistance  of  3,  one  inch 
will  be  sufficient  to  prevent  condensation. 

The  same  result  might  have  been  obtained  by  selecting  an  insulated  4-in.  concrete  slab 
having  a  U  of  less  than  0.275  from  Table  11,  Chapter  5.  This  4-in.  concrete  slab  with 
1-in.  rigid  insulation  has  a  U  of  0.23  which  is  safe. 


146 


L 


Chapter  8 

COOLING  LOAD 

Conditions  of  Comfort,  Design  Outside  Temperatures,  Com- 
ponents of  Heat  Gain,  Normal  Heat  Transmission,  Solar 
Heat  Transmission,  Sun  Effect  Through  Windows,  Heat 
Emission  of  Occupants,  Heat  Introduced  by  Outside  Air,  Heat 
Emission  of  Appliances 

OAD  calculations  for  summer  air  conditioning  are  more  complicated 
,  y  than  heating  load  calculations  for  the  reason  that  there  are  several 
more  factors  to  be  considered.  Because  of  the  variable  nature  of  some  of 
the  contributing  load  components  and  the  fact  that  they  do  not  neces- 
sarily impose  their  maximum  effect  simultaneously,  considerable  care 
must  be  exercised  in  determining  their  phase  relationship  in  order  that 
equipment  of  proper  capacity  may  be  selected  to  maintain  specified 
indoor  conditions. 

CONDITIONS  OF  COMFORT 

The  conditions  to  be  maintained  in  an  enclosure  are  variable  ^  and 
depend  upon  several  factors,  especially  the  outside  design  conditions, 
duration  of  occupancy  and  relationship  between  air  motion,  dry-bulb  and 
wet-bulb  temperatures.  Information  concerning  the  proper  effective 
temperature  to  be  maintained  is  given  in  Chapter  3,  where  are  also  tabu- 
lated the  most  desirable  indoor  conditions  to  be  maintained  in  summer  for 
exposures  over  40  min  (see  Table  2,  Chapter  3). 

DESIGN  OUTSIDE  TEMPERATURES 

Summer  dry-bulb  and  wet-bulb  temperatures  of  various  cities  are 
given  in  Table  1.  It  will  be  noted  that  the  temperatures  are  not  the  maxi- 
mums  but  the  design  temperatures  which  should  be  used  In  air  condition- 
ing calculations.  The  maximum  outside  wet-bulb  temperatures  as  given 
in  Weather  Bureau  reports  usually  occur  only  from  1  to  4  per  cent  of  the 
time,  and  they  are  therefore  of  such  short  duration  that  it  is  not  practical 
to  design  a  cooling  system  covering  this  range.  The  temperatures  shown 
in  Table  1  are  in  part  based  on  available  design  conditions  known  ^to  be 
successfully  applied  and  for  those  localities  where  this  information  is 
lacking  they  are  based  on  a  study  of  the  hourly  temperatures  in  New  York 
City  from  which  factors  were  derived  and  applied  to  the  average  maxi- 
mum dry-  and  wet-bulb  temperatures  for  other  cities.  This  study  covered 
a  twenty-year  record  of  Weather  Bureau  temperatures.  The  design 

147 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 


TABLE  1.    DESIGN  DRY-  AND  WET-BULB  TEMPERATURES,  WIND  VELOCITIES,  AND 
WIND  DIRECTIONS  FOR  JUNE,  JULY,  AUGUST,  AND  SEPTEMBER 


STATE 

CITY 

DESIGN 
DST-BULB 

DESIGN 
WET-BULB 

SUMMER  WIND 
VELOCITY 
MPH 

PREVAILING 
SUMMER  WIND 
DIRECTION 

Ala  

Birmingham  

Mobile 

95 
95 

78 
80 

5.2 

8.6 

S 

sw 

Ariz  

Phoenix  

105 

76 

6.0 

w 

Ark.      .     . 

Little  Rock 

95 

78 

7.0 

NE 

Calif. 

Los  Angeles 

90 

70 

6.0 

SW 

Colo. 

San  Francisco  
Denver 

90 
95 

65 
64 

11.0 
6.8 

sw 

S 

Conn  

New  Haven  

95 

75 

7.3 

S 

Dela. 
D.  C. 

Wilmington  

Washington 

95 
95 

78 
78 

9.7 
6.2 

sw 

S 

Fla. 

Jacksonville, 

95 

78 

8.7 

sw 

Tampa  

94 

79 

7.0 

E 

Ga  

Atlanta 

95 

75 

7.3 

NW 

Idaho     .  ... 

Savannah  
Boise.,  _....  

95 
95 

78 
65 

7.8 
5.8 

SW 

NW 

Ill  

Ind  _. 
Iowa  
Kansas  
Ky. 

Lav:  :: 

Maine.  
Md  
Mass. 
Mich  
Minn  ~ 
Miss.  
Mo  

Mont_ 

Chicago  _ 
Peoria  
Indianapolis  
Des  Moines  „  
Wichita  
Louisville  
New  Orleans  
Portland-  
Baltimore.-  
Boston  
Detroit  
Minneapolis.-  
Vicksburg  
Kansas  City.  
St.  Louis.  
Helena 

95 
95 
95 
95 
100 
95 
95 
90 
95 
92 
95 
95 
95 
100 
95 
95 

75 

76 
76 
77 
75 
76 
79 
73 
78 
75 
75 
75 
78 
76 
78 
67 

10.2 
8.2 
9.0 
6.6 
11.0 
8.0 
7.0 
7.3 
6.9 
9.2 
10.3 
8.4 
6.2 
9.5 
9.4 
7.3 

NE 
S 
SW 

sw 

S 

sw 
sw 

S 

sw 
sw 
sw 

SE 

sw 

S 

sw 
sw 

Nebr  
Nev  . 

N.  H. 
N.  J. 

N.  Y. 

Lincoln  
Reno  
Manchester  
Trenton  

Albany 

95 
95 
90 
95 
92 

75 
65 
73 
78 
75 

9.3 

7.4 
5.6 
10.0 

71 

S 

w 

NW 

sw 
s 

Buffalo  
New  York  

93 
95 

75 
75 

12.2 
12.9 

sw. 
sw 

N.  M.. 

Santa  Fe 

90 

65 

6  5 

SE 

N.  C. 

Asheville.  

90 

75 

5.6 

SE 

N.  Dak  _ 
Ohio  

Okla  
Ores.. 

psZ  :.  ... 

Wilmington  
Bismarck  
Cleveland  
Cincinnati  
Oklahoma  City  
Portland  
Philadelphia- 

95 
95 
95 
95 
101 
90 
95 

79 
73 

75 
78 
76 
65 
78 

7.8 
8.8 
9.9 
6.6 
10.1 
6.6 
97 

SW 

NW 
S 

sw 

s 

NW 
SW 

R.  I  „ 
S.  C  

S.  Dak  
Tenn.  

Pittsburgh  
Providence.  
Charleston  
Greenville.  
Sioux  Falls  
Chattanooga 

95 
93 
95 
95 
95 
95 

75 
75 
80 
76 
75 
77 

9.0 
10.0 
9.9 
6.8 
7.6 
6  5 

NW 
NW 
SW 
NE 
S 
SW 

Memphis  

95 

78 

7.5 

sw 

148 


CHAPTER  8.    COOLING  LOAD 


TABLE  1.     DESIGN  DRY  AND  WET-BULB  TEMPERATURES,  WIND  VELOCITIES,  AND 
WIND  DIRECTIONS  FOR  JUNE,  JULY,  AUGUST,  AND  SEPTEMBER  (Continued) 


STATE 


Crrr 


DESIGN 
DET-BCLB 


SUMMER  WIND  i    PBIVAUJNG 
VELOCITY     i  SUMMER  WIND 


Mm 

JLHRECriON 

Texas 

Dallas 

100 

78 

9.4 

s 

Galveston..  _  

95 

SO 

9.7 

s 

San  Antonio 

100 

78 

7.4 

SE 

Houston  

95 

78 

7.7 

S 

El  Paso,...  

100 

69 

6.9 

E 

Utah       

Salt  Lake  City  

95 

67 

8.2 

SE 

Vt 

Burlington  

90 

73 

8.9 

S 

Va 

Norfolk...... 

95 

78 

10.9 

S 

Richmond  

95 

78 

6.2 

SW 

Wash. 

Seattle.  

85 

65 

7.9 

S 

Spokane  .... 

90 

65 

6.5 

SW 

W.  Va  

Parkersburg  

•    95 

75 

5.3 

SE 

Wise. 

Madison.  

95 

75 

8.1 

SW 

Milwaukee.  

95 

75 

10.4 

s 

Wyo.   _  

Cheyenne.  

95 

65 

9.2 

s 

temperatures  given  are  not  exceeded  more  than  5  to  8  per  cent  of  the  time 
during  a  cooling  season  of  1200  hours  in  June,  July,  August  and  September 
for  an  average  year. 

COMPONENTS  OF  HEAT  GAIN 

A  cooling  load  determination  is  composed  of  five  components  which 
may  be  classified  in  the  following  manner: 

1.  Normal  heat  transfer  through  windows,  walls,  partitions,  doors,  floors,  ceilings,  etc. 

2.  Transfer  of  solar  radiation  through  windows,  walls,  doors,  skylights,  or  roof. 

3.  Heat  emission  of  occupants  within  enclosures. 

4.  Heat  introduced  by  infiltration  of  outside  air  or  controlled  ventilation. 

5.  Heat  emission  of  mechanical,  chemical,  gas,  steam,  hot  water  and  electrical 
appliances^located  within  enclosures. 

The  components  of  heat  gain,  classified  by  source  are  further  classified 
as  sensible  and  latent  heat  gain. 

The  first  two  components  fall  into  the  classification  of  sensible  heat 
gain,  that  is,  they  tend  to  raise  the  temperature  of  the  air  within  the 
structure.  The  last  three  components  not  only  produce  sensible  heat 
gain  but  they  may  also  tend  to  increase  the  moisture  content  of  the  air 
within  the  structure. 

Normal  Heat  Transmission 

By  normal  heat  transmission,  as  distinguished  from  solar  heat  trans- 
mission is  meant  the  transmission  of  heat  through  windows,  walls, 
partitions,  etc.  from  without  to  interior  of  enclosure  by  virtue  of  difference 
between  outside  and  inside  air  temperatures.  This  load  is  calculated  in  a 

149 


HEATING  VENTILATING   AIR  CONDITIONING   GUIDE  1938 


8 


I 


CO 


8 


nia 


CHAPTER  8.    COOLING  LOAD 


manner  similar  to  that  described  in  Chapter  7  (except  that  flow  of  heat 
is  reversed)  by  means  of  the  formula: 

Ht  =  AU(h-t)  (1) 

where 

Ht  =  heat  transmitted  through  the  material  of  wall,  glass,  floor,  etc.,  Btu  per  hour. 
A  —  net  inside  area  of  wall,  glass,  floor,  etc.,  square  feet. 
t  =  inside  temperature,  degrees  Fahrenheit. 
t0  =  outside  temperature,  degrees  Fahrenheit. 

U  =  coefficient  of  transmission  of  wall,  glass,  floor,  etc.,  Btu  per  hour  per  square  foot 
per  degree  Fahrenheit  difference  in  temperature  (Tables  3  to  13,  Chapter  5), 

Solar  Heat  Transmission 

Calculations  of  the  solar  heatjtransmitted  through  walls  and  roofs 
are  difficult  to  determine  because  of  periodical  character  of  heat  flow  and 
time  lag  due  to  heat  capacity  of  construction. 

The  variation  in  solar  intensity  normal  to  sun  in  Btu  per  square  foot 
per  hour  on  a  horizontal  surface,  and  on  east,  west,  and  south  walls  is 
given  in  Fig.  1.  The  curves  are  drawn  from  A.S.H.V.E.  Laboratory  data 
obtained  by  pyrheliometer,  are  based  on  sun  time  and  apply  for  a  per- 
fectly clear  day  on  August  1  at  a  north  latitude  of  40  deg.  A  study  of 
these  curves  discloses  the  periodic  relationship  and  wide  variation  in 
solar  intensity  on  various  surfaces.  It  will  be  observed  that  both  the  roof 
and  south  wall  radiation  curves  are  in  exact  phase  relationship  with  each 
other  and  that  whereas  the  east  and  west  wall  radiation  curves  overlap 
those  for  roof  and  south  wall,  they  do  not  overlap  each  other.  This  phase 
relationship  has  an  important  bearing  on  the  cooling  load.  Failure  to 
consider  the  periodical  character  of  heat  flow  resulting  from  diurnal 
movement  of  the  sun  and  the  lag  due  to  heat  capacity  of  the  structure, 
which  determine  the  timing  and  magnitude  of  the  heat  wave  flowing 
through  the  wall,  may  result  in  a  large  error  in  load  calculations. 

The  values  of  solar  intensity  appearing  in  Fig.  1  must  not  be  confused 
with  the  actual  heat  transmission  through  the  wall  for  much  of  this  heat 
intensity  on  an  outside  surface  is  in  part  reflected  and  in  part  wiped  off  by 
convection  to  the  outside  air.  A  mathematical  solution  for  the  deter- 
mination of  solar  heat  transmission  has  been  developed  but  the  equations 
involved  are  too  complex  for  practical  application.1  From  results  of  this 
investigation  and  earlier  studies,2  the  Research  Laboratory  has  prepared 
Tables  2,  3,  4  and  5  which  give  the  solar  intensity  (I)  for  various  hours  of 
the  day  against  walls  of  various  orientations  and  horizontal  surfaces  and 
the  solar  radiation  ( JG  )  transmitted  through  windows  of  various  orien- 
tations as  well  as  skylights  at  various  hours  of  the  day.  These  values  are 
shown  for  north  latitudes  from  30  to  45  deg. 

It  should  be  noted  that  the  values  for  (7)  represent  the  rate  of  solar 
intensity  impinging  against  and  not  transmitted  through  walls  and  roofs 
whereas  values  for  (7G)  represent  actual  rate  of  heat  transmission  through 
windows  and  skylights.  Since  the  amount  of  solar  intensity  actually 

1Heat  Transmission  as  Influenced  by  Heat  Capacity  and  Solar  Radiation,  by  F.  C.  Houghten,  J.  L. 
Blackshaw,  E.  W.  Pugh  and  Paul  McDennott  (A.S.H.V.E.  TRANSACTIONS,  Vol.  38,  1932,  p.  231). 

Absorption  of  Solar  Radiation  in  its  Relation  to  the  Temperature,  Color,  Angle  and  Other  Character- 
istics of  the  Absorbing  Surface,  by  F.  C.  Houghten  and  Carl  Gutberlet  (A.S.H.V.E.  TRANSACTIONS,  Vol. 
36,  1930,  p.  137).  -  .  _  .  .  . 

151 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


TABLE  2.  SOLAR  RADIATION  IMPINGING  AGAINST  WALLS  HAVING  SEVERAL  ORIENTATIONS, 

AND  A  HORIZONTAL  SURFACE,  AND  THE  RADIATION  TRANSMITTED  THROUGH  GLASS 

FOR  THE  SAME  ORIENTATIONS 

For  30  Deg  Latitude  on  the  twenty-first  of  July,  in  Btu  per  sqft  per  hour 


SUN 

NORTHEAST         EAST         SOUTHEAST        SOUTH        SOUTHWEST  i      WIST 

NORTHWEST 

HORIZONTAL 
SURFACE 

TnoB 

I 

IG   ,    I 

IG       I 

IG         I     '    1G    I     I         IG 

4:59 

0 

0           0 

0          0 

0               ;           ' 

! 

0 

0 

5:00;       1 

0.9         1 

0.9       0.3 

02             •           '           , 

0.01 

0.005 

6:00     47 

41          51 

44     ,    24 

17                            : 

9 

5 

7:00 

136 

106        160 

140     ,    90 

68     '                      ; 

68 

47 

8:00 

151 

122        205 

177       136 

105 

147 

116 

9:00 

127 

91        189 

156     ,  140 

104 

8          1 

214 

182 

10:00!     79 

47     ,    141 

103       122 

85 

31         12 

j 

265 

231 

11:00     21 

6     '     78 

45        85 

52 

45        21 

296 

261 

12:00 

•    36 

15        50        24 

36 

15 

305 

269 

1:00 

45        21 

85 

52 

78 

45 

21 

6 

296 

261 

2:00 

31         12 

122 

85 

141 

103 

79 

47 

265 

231 

3:001           ', 

8          1 

140 

104 

189 

156 

127 

91 

214 

182 

4:00 

136 

105 

205 

177 

151 

122 

147 

116 

5:00 

90 

68 

160 

140 

136 

106 

68 

47 

6:00j 

24 

17 

51 

44 

47 

41 

9 

5 

7:00; 

0.3 

0.2 

1 

0.9 

1 

0.9 

0.01 

0.005 

7:01 

; 

1 

j    o 

0 

0 

0 

0 

0 

0 

0 

TABLE  3.  SOLAR  RADIATION  IMPINGING  AGAINST  WALLS  HAVING  SEVERAL  ORIENTATIONS, 

AND  A  HORIZONTAL  SURFACE,  AND  THE  RADIATION  TRANSMITTED  THROUGH  GLASS 

FOR  THE  SAME  ORIENTATIONS 

For  85  Deg  Latitude  on  the  twenty-first  of  July,  in  Btu  per  sqft  per  hour. 


i 
STO    Nosn 

TtMB! 

HAST 

& 

5T 

Soum 

3EAST 

Soi 

JTH 

SOTJTI 

[WEST 

Wi 

car 

NORTI 

3WEST 

HORE 
SUR 

jONTAL 
PACT 

I 

IG 

/ 

IG 

I 

IG 

J 

'o 

"  7 

IG 

/ 

IG 

7 

IG 

7 

IG 

4:461       0 

0 

0 

0 

0 

0 

0 

0 

5:od       9 

8 

9 

8 

3 

2 

0.01 

0.007 

6:00!     67 

58 

72 

63 

35 

26 

15 

8 

7:00    142 

120 

174 

152 

103 

78 

77 

53 

8:00!   150 

120 

209 

181 

145 

114 

151 

120 

9:00    118 
10:00     60 

83 
32 

191 
143 

157 
104 

154 
139 

118 
101 

26 

55 

8 
27 

214 
264 

181 
230 

11:00       2 

0.1 

75 

43 

103 

67 

72 

41 

291 

256 

12:00 

55 

28 

78 

46 

55 

28 

300 

265 

l:oJ 

72 

41 

103 

67 

75 

43 

2 

0.1 

291 

256 

2:00 

55 

27 

139 

101 

143 

104 

60 

32 

264 

230 

3:00! 

26 

8 

154 

118 

191 

157 

118 

83 

214 

181 

4:00| 

145 

114 

209 

181 

150 

120 

151 

120 

5:00; 

103 

78 

174 

152 

142 

120 

77 

53 

6:00! 

35 

26 

72 

63 

67 

58 

15 

8 

7:00 

3 

2 

9 

8 

9 

8 

0.01 

0.007 

7:14 

0 

0 

0 

0 

0 

0 

0 

0 

152 


CHAPTER  8.    COOLING  LOAD 


TABLE  4.   SOLAR  RADIATION  IMPINGING  AGAINST  WALLS  HAVING  SEVERAL  ORIENTATIONS 

AND  A  HORIZONTAL  SURFACE,  AND  THE  RADIATION  TRANSMITTED  THROUGH  GLASS 

FOR  THE  SAME  ORIENTATIONS 

For  40  Deg  Latitude  on  the  twenty-first  of  July,  in  Bin  per  sqft  per  hour. 


SUN 
TIME 

NORTHEAST 

EAST 

SOUTHEAST        SOUTH        SOUTHWEST         WEST        ISORTI 

,  HORIZONTAL 
IWEST  i     SURFACE 

T 

j. 

G 

/G    ,     J 

JG          L 

JG         7 

7G           l 

'G 

4:31       0 

0 

0 

0         0  :       0                        ' 

\       0         0 

5:00,     14 

12 

14 

12 

- 

3         i       ;       ; 

1     1 

0.2 

6:00 

72 

63 

80 

70 

40        29 

19        11 

7:001   143 

120 

180 

158 

112 

87 

;     82 

57 

8:00    143 

111 

211 

182 

155 

124 

8 

2 

152 

121 

9:00 

104 

69 

192 

158 

168 

133 

46 

22 

| 

] 

213 

178 

10:00 

46 

22 

143 

104 

156 

117 

77 

45 

! 

j 

255 

225 

11:00 

75 

43 

121 

83 

95 

60 

15  ,      4 

i 

284 

249 

12:00 

73 

42 

103 

67 

73  1     42 

293 

258 

1:00 

15 

4 

95 

60 

121 

83 

75 

43 

284 

249 

2:00 

77 

45 

156 

117 

143 

104 

46 

22 

25S 

225 

3:00 

46 

22 

168 

133 

192 

158 

104 

69 

213 

178 

4:00 

8 

2 

155 

124 

211 

182 

143 

111 

152 

121 

5:00 

112 

87 

180 

158 

143 

120 

82 

57 

6:00 

i 

40 

29 

80 

70 

72 

63 

19 

11 

7:00 

5         3 

14 

12 

14 

12 

1 

0.2 

7:29 

0         0 

0 

0 

0 

o 

0 

0 

1 

TABLE  5.   SOLAR  RADIATION  IMPINGING  AGAINST  WALLS  HAVING  SEVERAL  ORIENTATIONS 

AND  A  HORIZONTAL  SURFACE,  AND  THE  RADIATION  TRANSMITTED  THROUGH  GLASS 

FOR  THE  SAME  ORIENTATIONS 

For  45  Deg  Latitude  on  the  twenty-first  of  July,  in  Btu  per  sqft  per  hour. 


SUN 
TIME 

NORTHEAST 

EAST 

SOUTHEAST 

SOUTH 

SOUTHWEST 

WEST 

NOETHWEST 

HORIZONTAL 

SUMACS 

J 

*G 

J 

*G 

J 

'G 

J 

*G 

7 

'G 

I 

'G 

I 

*G 

r 

*G 

4:26 

0 

0 

0 

0 

0 

0 

0 

0 

5:00 

25 

22 

24 

21 

9 

6 

2 

07 

6:00 

89 

77 

99 

88 

52 

39 

26 

15 

7:00 

149 

125 

194 

170 

125 

99 

90 

63 

8:00 

140 

109 

219 

189 

171 

139 

22 

8 

156 

123 

9:00 

92 

58 

194 

160 

183 

148 

65 

36 

210 

177 

10:00 

33 

13 

144 

106 

171 

134 

98 

63 

251 

217 

11:00 

75 

43 

139 

101 

121 

83 

32 

13 

274 

240 

12:00 

91 

67 

128 

90 

91 

67 

282 

247 

1:00 

32 

13 

121 

83 

139 

101 

75 

43 

274 

240 

2:00 

98 

63 

171 

134 

144 

106 

33 

13 

251 

217 

3:00 

65 

36 

183 

148 

194 

160 

92 

58 

210 

177 

4:00 

22 

8 

171 

139 

219 

189 

140 

109 

156 

123 

5:00 

125 

99 

194 

170 

144 

125 

90 

63 

6:00 

52 

39 

99 

88 

89 

77 

26 

15 

7:00 

9 

6 

24 

21 

25 

22 

2 

0.7 

153 


HEATING  VENTILATING  AIR  CONDITIONING   GUIDE  1938 


transmitted  through  a  surface  depends  upon  the  nature  of  the  exterior 
surface  of  wall  or  roof  construction,  it  is  necessary,  in  order  to  determine 
actual  amount  of  solar  heat  transmission,  to  apply  correction  factors  to 
the  values  of  (I).  Solar  radiation  factors  and  solar  absorption  coefficients 
have  been  determined3  as  indicated  in  Fig.  2  and  Table  6  respectively. 


0.20 


0.18 


0.14 


U.Q.I: 

I 

SL. 


-U 


C0.08 


0.06 


0.04 


0.02 


0.1          O2          O3  O4  O5          O6  07 

WALL  TRANSMISSION  COEFFICIENT,  Uw 

FIG.  2.    SOLAR  RADIATION  FACTORS 


.8 


The  solar  heat  conduction  through  a  wall  or  roof  exposed  to  the  sun 
may  be  expressed  by  the  formula: 


-  A Fal 


(2) 


where 


HR  —  Solar  heat  transmission,  Btu  per  hour. 
A  -  Area  of  wall  or  roof,  square  feet. 

F  =  Percentage  (expressed  as  a  decimal)  of  the  absorbed  solar  radiation  which  is 

transmitted  to  the  inside  (Fig.  2) . 
a  =  Percentage  (expressed  as  a  decimal)  of  the  incident  solar  radiation  which  is 

absorbed  by  the  surface  (Table  6). 
/  -  Actual  intensity  of  solar  radiation  striking  surface.  Btu  per  hour  per  square 

foot  (Tables  2r  3,  4  and  5). 


*A  Rational  Heat  Gain  Method  for  the  Determination  of  Air  Conditioning  Cooling  Loads,  by  F.  H. 
Faust,  L.  Levine  and  F.  0.  Urban  (A.S.H.V.E.  TRANSACTIONS,  Vol.  41.  1935?  £  327)7 

154 


CHAPTER  8.    COOLING  LOAD 


The  total  amount  of  heat  conducted  through  a  wall  exposed  to  the  sun 
is  the  sum  of  Ht  and  H&  from  Formulas  1  and  2. 

The  calculation  of  heat  transmission  through  walls  and  roofs  does  not 
take  into  consideration  the  heat  capacity  of  the  structure  nor  the  con- 

TABLE  6.     SOLAR  ABSORPTION  COEFFICIENTS  FOR  DIFFERENT  BUILDING  MATERIALS 


SURFACE  MATERIAL 


ABSORPTION  COEFFICIENT 

(a) 


Very  Light  Colored  Surfaces 
White  stone 

Very  light  colored  cement 
White  or  light  cream-colored  paint 


0.4 


Medium  Dark  Surfaces 
Asbestos  shingles 
Unpainted  wood 
Brown  stone 
Brick  and  red  tile 
Dark-colored  cement 
Stucco 
Red,  green  or  gray  paint 


0.7 


Very  Dark  Colored  Surfaces 
Slate  roofing 
Tar  roofing  materials 
Very  dark  paints 


0.9 


sequent  time  lag  in  the  transmission  of  heat.  In  the  case  of  massive  walls 
the  time  lag  may  amount  to  several  hours4.  Thus  in  many  cases  the  wall 
transmission  cannot  be  added  directly  to  the  cooling  load  from  dther 
sources  because  the  peak  of  the  wall  transmission  load  may  not  coincide 

TABLE  7.   TIME  LAG  IN  TRANSMISSION  OF  SOLAR  RADIATION  THROUGH  WALLS  AND  ROOFS 


TYPE  AND  THICKNESS  OF  WAIJ.  OB  ROOF 

Tom  LAG, 
HOTJHS 

2-in.  oine 

\Yz 

—  i*i.  ^.*^^-  —  -    

o-in.  concrete 

3 

4rin.  gypsum 

2^ 

3-in.  concrete  and  1-in.  cork.           .       ~  

2 

2-in.  iron  and  cork  (equivalent  to  %-in.  concrete  and  2.15-in.  cork)  
4-in.  iron  and  cork  (equivalent  to  5J^-in.  concrete  and  1.94-in.  cork)        .  ,  . 

2^ 
7H 

8-in.  iron  and  cork  (equivalent  to  16-in.  concrete  and  1.53-in.  cork)  

19 

22-in.  brick  and  tile  wall            

10 

with  the  peak  of  the  total  cooling  load  and  may  even  occur  after  the 
cooling  system  has  been  shut  down  for  the  day.  The  data  in  Table  7  were 
taken  from  A.S.H.V.E.  research  papers  and  whereas  they  result  from  a 
study  of  experimental  slabs,  they  give  an  approximate  idea  of  the  time  lag 
to  be  expected  in  various  structures. 


<Loc.  Cit.  Notes  1  and  2. 


155 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 


Sun  Effect  Through  Windows 

Windows  present  a  problem  somewhat  different  from  that  of  opaque 
walls,  because  they  permit  a  large  percentage  of  the  solar^  energy  to  pass 
through  undiminished  ;  only  a  small  percentage  (approximately  10  per 
cent)  is  reflected.  This  fact  permits  the  solar  heat  gain  through  windows 
to  be  expressed  by  the  simple  formula: 


where 


(3) 


HG  =  Solar  radiation  transmitted  through  a  window,  Btu  per  hour. 
^G  =  Area  of  glass,  square  feet. 

^G  —  Amount  of  solar  radiation  transmitted  directly  through  the  glass,  Btu  per  hour 
per  square  foot  (Tables  2,  3,  4  and  5). 

Values  for  solar  heat  transmission  through  glass  as  determined  by 
Formula  3  apply  only  to  unshaded  windows.  Tests  at  the  A.S.H.V.E. 
Research  Laboratory*  have  determined  the  percentages  of  heat  from 
solar  radiation  actually  delivered  to  a  room  with  bare  windows  and  with 
various  types  of  outdoor  and  indoor  shading.  The  data  in  Table  8  are 
taken  from  these  tests. 

TABLE  8.   SOLAR  RADIATION  TRANSMITTED  THROUGH  BARE  AND  SHADED  WINDOWS 


TTPB  OF  APPUBTENANCB 

FINISH 
FACING 

SUN 

PEB  CENT 
TO  ROOM 

Bare  window  glass..  ..        

97 

Canvas  awniner      .                                                      

Plain 

28 

Canvas  awning 

Aluminum 

22 

Inside  shade,  fully  drawn  

Aluminum 

45 

Inside  shade,  one-half  drawn  .     .              

Buff 

68 

Inside  Venetian  blind,  fully  covering  window,  slats  at  45  deg  
Outside  Venetian  blind,  fully  covering  window,  slats  at  45  deg.... 

Aluminum 
Aluminum 

58 
22 

The  percentage  values  in  this  table  were  obtained  by  dividing  the  total 
amount  of  heat  actually  entering  through  the  shaded  window  by  the  total 
amount  of  heat  calculated  to  enter  through  a  bare  window  (solar  radiation 
plus  glass  transmission  based  on  observed  outside  glass  temperature). 
For  bare  windows  on  which  the  sun  shines,  the  transmission  of  heat  from 
outside  air  to  glass  is  small  or  negative  because  the  glass  temperature  is 
raised  by  the  solar  radiation  absorbed.  Therefore,  in  calculating  the 
total  heat  gain  through  windows  on  the  sunny  sides  of  buildings,  it  is 
sufficiently  accurate  to  determine  the  total  cooling  load  due  to  the  win- 
dow, as  the  solar  radiation  times  the  proper  factor  from  Table  8  and  to 
neglect  the  heat  transmission  through  the  glass  caused  by  the  difference 
between  the  temperatures  of  the  inside  and  outside  air. 

Although  Table  8  shows  that  97  per  cent  of  the  heat  from  solar  radia- 
tion is  delivered  to  a  room  through  bare  window  glass,  more  recent  tests6 


*Radiation  of  Energy  Through  Glass,  by  J.  L.  Blackshaw  and  F.  C.  Houghten  (A.S.H.V.E.  TRANS- 
ACTIONS, Vol.  40,  1934,  p.  93).  Studies  of  Solar  Radiation  Through  Bare  and  Shaded  Windows,  by  F.  C. 
Houghten,  Carl  Gutberlet,  and  J.  L.  Blackshaw  (A.S.H.V.E.  TRANSACTIONS,  Vol.  40,  1934,  p.  101). 

•Cooling  Requirements  of  Single  Rooms  in  a  Modern  Office  Building,  by  F.  C.  Houghten,  Carl  Gutberlet, 
and  Albert  J.  Wahl  (A.S.H.V.E.  TRANSACTIONS,  Vol.  41,  1935,  p.  53). 

156 


CHAPTER  8.    COOLING  LOAD 


have  indicated  that  in  the  case  of  a  building  having  floors  of  high  heat 
capacity  such  as  concrete  floors  on  which  the  solar  radiation  falls,  approxi- 
mately one-half  of  the  heat  entering  a  bare  window  is  absorbed  by  the 
floor  and  does  not  immediately  become  a  part  of  the  cooling  load  but  is 
delivered  back  to  the  air  in  the  building  at  a  slow  rate  over  a  period  of 
24  hours  or  longer. 

The  maximum  solar  intensity  on  any  surface  is  of  limited  duration  as 
shown  in  Fig.  1.  In  the  case  of  windows  the  total  energy  impinging  on  the 
glass  before  and  after  the  time  of  maximum  intensity  is  further  reduced 
by  increased  shading^  of  the  glass  from  the  frame,  or  wall.  The  cooling 
load  due  to  solar  radiation  therefore  does  not  have  to  be  calculated  as  a 
steady  load.  Another  point  which  should  be  noted  is  that  the  maximum 
solar  radiation  load  on  the  east  wall  occurs  early  in  the  morning  when  the 
outside  temperature  is  low. 

In  a  paper7  by  the  A.S.H.V.E.  Research  Laboratory  it  was  shown  that 
ordinary  double  strength  window  glass  transmits  no  measurable  amount 
of  energy  radiated  from  a  source  at  500  F  or  lower;  that  it  transmits  only 
6.0  and  12.3  per  cent  of  the  total  radiation  from  surfaces  at  700  F  and 
1000  F,  respectively;  and  that  it  transmits  65.7  per  cent  of  the  radiation 
from  an  arc  lamp,  76.3  per  cent  of  the  radiation  from  an  incandescent 
tungsten  lamp,  and  89.9  per  cent  of  the  radiation  from  the  sun.  Thus, 
glass  windows  in  a  room  constitute  heat  traps,  which  allow  rather  free 
transmission  of  radiant  energy  into  the  room  from  the  sun  to  warm  objects 
in  it,  but  do  not  allow  the  transmission  of  re-radiated  heat  from  these 
same  objects. 

Tests  have  been  made  which  indicated  that  sunshine  through  window 
glass  is  the  most  important  factor  to  contend  with  in  the  cooling  of  an 
office  building.  At  times  it  was  shown  to  account  for  as  much  as  75  per 
cent  of  the  total  cooling  necessary.  Because  of  the  importance  of  the 
sunshine  load,  cooling  systems  should  be  zoned  so  that  the  side  of  the 
building  on  which  the  sun  is  shining  can  be  controlled  separately  from  the 
other  sides  of  the  building.  If  buildings  are  provided  with  awnings  so 
that  the  window  glass  is  shielded  from  sunshine,  the  amount  of  cooling 
required  will  be  reduced  and  there  will  also  be  less  difference  in  the  cooling 
requirements  of  different  sides  of  the  building.  The  total  cooling  load 
for  a  building  exposed  to  the  sun  on  more  than  one  side  is  of  course  less 
than  the  sum  of  the  maximum  cooling  loads  in  the  individual  rooms  since 
the  maximum  solar  radiation  load  on  the  different  sides  occurs  at  different 
times.  In  determining  the  total  cooling  load  for  a  building  if  the  time 
when  the  maximum  load  occurs  is  not  obvious,  the  load  should  be  calcu- 
lated for  various  times  of  day  to  determine  the  times  at  which  the  sum 
of  the  loads  on  the  different  sides  of  the  building  is  a  maximum. 

Heat  Emission  of  Occupants 

The  heat  and  moisture  given  off  by  human  beings  under  various  states 
of  activity  are  shown  in  Figs.  8  to  11  and  Table  4  of  Chapter  3.  It  will  be 
observed  that  the  rate  of  sensible  and  latent  heat  emission  by  human 
beings  varies  greatly  depending  upon  state  of  activity.  In  many  applica- 
tions this  component  becomes  a  large  percentage  of  total  load. 

Txx:.  Cit.  Note  5. 

157 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 

Heat  Introduced  by  Outside  Air 

An  allowance  must  be  made  for  the  heat  and  moisture  in  the  outside 
air  introduced  for  ventilation  purposes  or  entering  the  building  through 
cracks,  crevices,  doors,  and  other  places  where  infiltration  might  occur. 

The  volume  of  air  entering  due  to  infiltration  may  be  estimated  from 
data  given  in  Chapter  6.  Information  on  the  amount  of  outside  air 
required  for  ventilation  will  be  found  in  Chapter  3 . 

In  the  event  the  volume  of  air  entering  an  enclosure  due  to  infiltration 
exceeds  that  required  for  ventilation,  the  former  should  be  used  as  a  basis 
for  determining  the  portion  of  the  load  contributed  by  outside  air.  Where 
volume  of  air  required  for  ventilation  exceeds  that  due  to  infiltration  it  is 
assumed  that  a  slight  positive  pressure  will  exist  within  the  enclosure  with 
a  resulting  exfiltration  instead  of  infiltration.  In  this  case  the  air  required 
for  ventilation  is  used  in  determining  outside  air  load. 

The  sensible  heat  gain  resulting  from  the  outside  air  introduced  may  be 
determined  by  the  following  formula: 

Hs  =  0.24  X  60  do  Q  (to  -  0  (4) 

where 

Hs  —  sensible  heat  to  be  removed  from  outside  air  entering  the  building,  Btu  per  hour. 

Q  =  volume  of  outside  air  entering  building,  cubic  feet  per  minute. 

do  -  density  of  air,  pounds  of  dry  air  per  cubic  foot  at  temperature  t0. 

to  =  temperature  of  outside  air,  degrees  Fahrenheit. 

t  =  temperature  of  inside  air,  degrees  Fahrenheit. 

The  total  heat  gain  resulting  from  outside  air  introduced  may  be  deter- 
mined by  the  following  formula: 

H  =  60  do  Q  (h0  -  h)  (5) 

where 

H  —  total  heat  to  be  removed  from  outside  air  entering  the  enclosure,  Btu  per  hour. 
Q  =  volume  of  outside  air  entering  enclosure,  cubic  feet  per  minute. 
do  =  density  of  air,  pounds  of  dry  air  per  cubic  foot  of  air  (at  temperature  /0). 
fio  =  heat  content  of  mixture  of  outside  dry  air  and  water  vapor,  Btu  per  pound  of 

dry  air  (at  temperature  t0). 
h  =  heat  content  of  mixture  of  inside  dry  air  and  water  vapor,  Btu  per  pound  of 

dry  air  (at  temperature  t). 

The  latent  heat  gain  resulting  from  outside  air  introduced  may  be 
determined  by  the  following  formula: 

Hi  =  H  -  Hn  (6) 

where 

Hi  -  latent  heat  to  be  removed,  Btu  per  hour. 
H  —  total  heat  to  be  removed,  Btu  per  hour. 
Hs  =  sensible  heat  to  be  removed,  Btu  per  hour. 

Heat  Emission  of  Appliances 

Heat  generating  appliances  which  give  off  either  sensible  heat  or  both 
sensible  and  latent  heat  in  an  air  conditioned  enclosure  may  be  divided 

158 


CHAPTER  8.    COOLING  LOAD 


into  three  general  classes  of  equipment  or  devices: 

1.  Electrical  appliances. 

2.  Gas  appliances. 

3.  Steam  heating  appliances. 

In  the  first  group  may  be  found  such  devices  as  lights,  motors,  toasters, 
waffle  irons,  etc.  The  capacities  of  most  electrical  devices  may  be 
determined  from  the  watt  capacity  indicated  on  their^  name  plates. 
The  Btu  equivalent  of  heat  generated  per  hour  is  determined  by  multi- 
plying the  watt  capacity  by  3.4  (one  watthour  is  equivalent  to  3.413  btu). 

The  capacities  of  electric  motors  are  usually  expressed  in  terms  of 
horsepower  instead  of  watts.  If  the  motor  efficiency  is  known,  the  watts 
input  may  be  calculated  from  the  formula: 

=  746  (hp)  (7) 

n 

where 

P  =  motor  input,  watts. 
hp  —  motor  load,  horsepower. 
n  =  motor  efficiency  (expressed  as  a  decimal). 

When  the  motor  efficiency  is  not  known  the  heat  equivalent  of  ej?c^ic?;1 
input  can  be  approximately  determined  by  applying  data  given  in  1  able  V>. 

HEAT  GENERATED  BY  MOTORS 


NAMEPLATE  EATING  HORSEPOWER 

TTHUT  GAIN  IN  BTTJ  PEE  HOUR  PEE  HORSEPOWER 

Connected  Load  in  Same  Room 

Connected  Load  Outside  of  Room 

Ysto  % 
Hto3 
3    to  20 

4250 
3700 
2950 

1700 
1150 
400 

In  the  second  group  belong  such  appliances  as  coffee  urns,  gas  ranges, 
ste£n  tables,  broilers,  hot  plates,  etc.  For  heat  generating  capacities 
of  such  appliances  refer  to  Table  10. 

Considerable  judgment  must  be  exercised  in  the  use  of  data  given  in 
Table  10.  Consideration  must  be  given  to  time  of  day  when  appliances 
are  used  and  the  heat  they  contribute  to  the  space  at  time  of  peak .load. 
Only  those  appliances  in  use  at  the  time  of  the  peak  load  need  be  con- 
sidered. Consideration  must  also  be  given  to  the  way  appliances  ar 
installed,  whether  products  of  combustion  are  vented  to  a  flue,  whethe 
products  of  combustion  escape  into  the  space  to  be  conditioned  or  whethe 
appliances  are  hooded  allowing  part  of  the  heat  to  escape  through  « 
stSk?onnected  with  the  hood.  There  are  no  generally  acceptoi  dafe 
available  on  the  effects  of  venting  and  shielding  heating  appliances  but  i 
TbeSed  tiiat  when  the  appliances  are  properly  hooded wi*  a  pomtij 
fan  exhaust  system  through  the  hood  that  50  per  cent  of  the  heat  will  b^ 
SnvSed up  SS  the  hood  and  the  balance  of  50  per  cent  will  be  dissipate. 
S  the  Sac?  to  be  conditioned.  Where  latent  as  well  as  sensible  heat  i 
Sv?n  off,  h is usually  safe  to  assume  that  all  latent  heat  will  be  remove, 
by  a  properly  designed  and  operated  vent  or  hood. 


HEATING  VENTILATING   AIR  CONDITIONING   GUIDE  1938 

TABLE  10. 

HEAT  GAIN  FROM  VARIOUS  SOURCES 

SOURCE 

BTU  PK. 

s.  HOUR 

Sensible    La 

tent      Total 

Electric  Heating  Equipment 

Electrical  Equipment  —  Dry  Heat—  No  Evaporated  \\  ater  _  - 
Electric  Oven  —  Baking  —  -  
Electric  Equipment—  Heating  Water—  Stewing,  Boiling,  etc  
Electric  Lights  and  Appliances  per  Watt  (Dry  Heat)_  
Electric  Lights  and  Appliances  per  Kilowatt  (Dry  Heat)  —  
Electric  Motors  per  Horsepower  

100% 
80% 
50% 
3.4 
3413 
2546 
90% 

1200 
600 
* 
* 
8000 
1025 
300 
850 
3200 
* 
* 
2050 
2050 

0% 
20% 
50% 
0 
0 
0 
10% 
2000 
1200 
600 

* 
2000 
0 
800 
0 
1300 
* 
* 
0 
0 

100% 
100% 
100% 
3.4 
3413 
2546 
100% 

2400 
1200 
3400 
7500 
10000 
1025 
1100 
850 
4500 
4600 
9000 
2050 
2050 

Coffee  Urn  —  Large,  IS  in.  Diameter—  Single  Drum.—  -  — 

Coffee  Urn—  Approx.  Connected  Load  per  Gallon  of  Capacity  
Electric  Range  —  Small  Burner.  

Electric  Range""  Large  Burner                               -  .......   —  ~   ...........—-.  — 

Electric  Range  —  Oven..  -  -  

Electric  Ra.nze—  AVarming  Compartment                         —  .......  ,-  -,.,  ..  

Steam  Table—  Per  Square  Foot  of  Top  Surface  

Baker's  Oven    Per  Cubic  Foot  of  Volume                 .  --—.  .............  ......   ...*——....... 

Frying  Griddles—  Per  Square  Foot  of  Top  Surface  

Hair  Dryer  in  Beauty  Parlor—  ^600  w  

Permanent  Wave  Machine  in  Beauty  Parlor—  24-25  w  Units  

Gas  Burning  Equipment 

Gas  Equipment  —  Dry  Heat  —  No  Water  Evaporated  
Gas  Heated  Oven  —  Baking.                              •     .  -.  •—  «  

90% 
67% 
50% 

12000 
5000 

* 
* 
5000 
3000 
500 
2500 
400 
540 
2250 
2250 

4500 
2250 
900 
540 
135 

10% 
33% 
50% 

6000 
5000 

* 
* 
5000 
3000 
500 
2500 
900 
60 
250 
250 

500 
250 
100 
60 
15 

100% 
100% 
100% 
10000 
18000 
10000 
12000 
10000 
18000 
250 
100000 
100 
250 
2500 
10000 
6000 
1000 
5000 
1300 
600 
2500 
2500 
5000 
3000 
3000 
1800 
3000 
1800 
5000 
3000 
5000 
2500 
1000 
600 
150 

Gas  Equipment—  Heating  Water—  Stewing,  Boiling,  etc  
Stove,  Domestic  Type  —  No  Water  Evaporated  —  Per  Medium  Size  Burner.  
Gas  Heated  Oven*—  Domestic  Type     —    - 

Stove  Domestic  Type—  Heating  Water—  Per  Medium  Size  Burner    ...„  -      -  

Residence  Gas  Range  —  Giant  Burner  (About  5J^j  in.  Diameter*)  ..  ,- 

Residence  Gas  Range  —  Medium  Burner  (About  4  in,  Diameter)           ,..,    

Residence  Gas  Range  —  Double  Oven  (Total  Size  18  in.  x  18  in.  x  22  in.  High)  
Residence  G&s  Range—  "Pilot                                .  ......——  .......  ...,,„„-,-„  ,  T,™-,  

Restaurant  Range—  4  Burners  and  Oven  _.  —  

Cast-iron  Burner  —  Low  Flame  —  Per  Hole....-—  ~  —  

Cast-iron  Burner  —  High  Flame  —  Per  Hole™.    ..   

Sinnneritjg  Burner                                               -  —  ............ 

Coffee  Urn  —  Large,  18  in.  Diameter—  Single  Drum  

Coffee  Urn  —  Small,"  12  I'TV  Diameter  —  Single  PT™  

Coffee  Urn  —  Per  Gallon  of  Rated  Capacity  ..  .-.  

Egg  Boiler  —  Per  Egg  Compartment  —  

Steam  Table  or  Serving  Table  —  Per  Square  Foot  of  Top  Surface    ,.-  ...  r  ,,„_ 

Dish  Warmer  —  Per  Square  Foot  of  Shelf,-    ^  —  ,-  -,  -        -* 

Cigar  Lighter—  Continuous  Flame  Type-  —  - 

Curling  Iron  Heater                                           ~  -  

Bunsen  Type  Burner  —  Large  —  Natural  Gas  

Bunsen  Type  Burner~—  Large-—  •  Artificial  Gas.....................  ...................  .............. 
Bunsen  Type  Burner~~SmalV~~Natural  Gas 

Bunsen  Type  Burner  —  Small  —  Artificial  Gas  -,-„  ,-,--,-    

Welsbacli  "Burner  —  Natural  Gas                                          — 

Welsbach  Burner  —  Artificial  Gas        

Fish-tail  Burner  —  Natural  Gas                                         ,  .,....„,,  ^  -,  -—-,  -,  -T  

Fish-tail  Burner  —  Artificial  Gas.                 .    .  —  —  

Lighting  Fixture  Outlet  —  Large,  3  Mantle  480  C.P  

Lighting  Fixture  Outlet  —  Small,  1  Mantle  160  C.P  

One  Cubic  Foot  of  Natural  Gas  Generates 

One  Cubic  Foot  of  Artificial  Gas  Generates  

One  Cubic  Foot  of  Producer  Gas  Generates-  _  

Steam  Heated  Equipment 


Steam  Heated  Surface  Not  Polished  —  Per  Square  Foot  of  Surface  
Steam  Heated  Surface  Polished  —  Per  Square  Foot  of  Surface  

330 
130 
80 
400 
220 
110 
2000 
1200 
2500 
300 

0 
0 
0 
0 
0 
0 
2000 
1200 
2500 
800 

330 
130 
80 
400 
220 
110 
4000 
2400 
5000 
1100 

Insulated  Surface,  Per  Square  Foot  ....  .........  _...  ...u.^.  
Bare  Pipes,  Not  Polished  Per  Square  Foot  of  Surface.-    

Bare  Pipes,  Polished  i*er  Square  Foot  of  Surface.  ,„  

Insulated  Pipes,  Per  Square  Foot—                .  -  

Coffee  Urn—  Large(  18"in.  Diameter  —  "Single  PniTTL 

Coffee  Urn  —  Small,  12  in.  Diameter  —  Single  Drum  
Egg  Boiler  —  Per  Egg  Compartment             ..                                   ... 

Steam  Table  —  Per  Square  Foot  of  Top  Surface  

Miscellaneous 


Heat  Liberated  By  Food  per  person,  as  in  a  Restaurant 

Heat  Liberated  from  Hot  Water  used  direct  and  on  towels  per  hour — Barber  Shops  | 


30 
100 


30 
200 


60 
300 


'"Per  cent  sensible  and  latent  heat  depends  upon  use  of  equipment;  dry  heat,  baking  or  boiling. 

160 


CHAPTER  8.    COOLING  LOAD 


GENERAL 

From  the  foregoing  discussion  it  is  obvious  that  the  determination  of 
the  maximum  cooling  load  is  rather  complicated  by  reason  of  the  variable 
nature  of  contributing  load  components.  If  the  time  when  the  maximum 
load  occurs  is  not  obvious  the  load  should  be  calculated  for  various  times 
of  the  day  to  determine  the  probable  time  at  which  the  sum  of  the  various 
component  loads  is  a  maximum. 

Application  of  the  foregoing  data  in  determining  cooling  load  require- 
ments is  illustrated  in  Example  1. 


Store  room 


/<- 


b 

fe 


Ceiling  height,  12-V 


-54-'0"- 


8'x6'  14'x6'  H'x6' 

FIG.  3.    PLAN  DIAGRAM  OF  CLOTHING  STORE 


14'x6' 


Example  1.  Determine  cooling  load  requirements  for  a  clothing  store  illustrated  in 
Fig.  3  and  located  in  Cleveland,  Ohio,  Latitude  40  deg.  This  is  a  one-story  building 
located  on  a  corner  and  it  faces  south  and  west.  Assume  building  on  east  and  north 
sides  conditioned. 

Wall  construction,  8  in.  hollow  tile,  4  in.  brick  veneer,  plaster  on  walls,  U  =  0.33 
(Table  4,  Wall  38  B,  Chapter  5). 

Roof  construction,  2  in.  concrete,  %  in.  rigid  insulation,  metal  lath  and  plaster 
ceiling,  U  =  0.26  (Table  11,  Wall  2  J,  Chapter  5). 

Floor,  maple  flooring  on  yellow  pine,  no  ceiling  below,  U  =  0.34  (Table  8,  Wall 

1  D,  Chapter  5). 

Partition,  wood  lath  and  plaster  on  both  sides  of  studding,  U  =  0.34  (Table  6, 

Wall  77  B,  Chapter  5). 

Show  windows,  provided  with  awnings  and  thin  panel  partition  at  rear. 

Front  doors,  2  ft  6  in.  x  7  ft  (glass  panelled),  U  -  1.13  (Table  13  A,  Chapter  5). 

Side  door,  3  ft  x  7  ft  (solid,  1%  in.  thick),  U  =  0.51  (Table  13  B,  Chapter  5), 

Occupancy,  10  clerks,  40  patrons. 

Lights,  4200  w. 

Outside  design  conditions,  dry-bulb  95  F;  wet-bulb  75  F. 

Inside  design  conditions,  dry-bulb  80  F;  wet-bulb  67  F. 

Basement  temperature,  85  F. 

Store  room  temperature,  88  F. 

161 


HEATING   VENTHATINO  AIR  CONDITIONING   GUIDE  1938 


Solution:  The  normal  heat  transmission  through  various  surfaces  shown  in  load 
calculations  are  determined  by  application  of  Formula  1. 

It  is  quite  obvious  from  the  shape  and  exposure  of  this  store  that  the  maximum  sun 
load  will  exist  on  the  west  wall.  Since  the  west  wall  has  a  large  glass  area  with  a  negligible 
time  lag,  the  peak  load  may  be  expected  at  4:00  p.m.  at  which  time,  from  Table  4, 
IG  -  182.  JG  f°r  south  glass  at  4:00  p.m.  is  2.  Because  of  the  small  amount  of  solar 
radiation  transmitted  through  the  south  glass,  the  transmission  due  to  temperature 
difference  has  also  been  included.  Assuming  time  lag  in  roof  and  walls  to  be  2  hours,  the 
corresponding  values  for  7  for  south  and  west  walls  and  roof  will  be  those  shown  in  Table 
4  for  2:00  p.m.  They  are  respectively  77, 143  and  258.  A  time  lag  of  1  hour  was  assumed 
for  the  west  door  amounting  to  I  =  192.  By  substituting  these  values  in  equations  2 
and  3  the  solar  heat  load  is  determined. 

To  determine  the  heat  gain  from  the  outside  air  it  is  necessary  first  to  determine  the 
volume  of  the  outside  air  to  be  introduced.  Since  the  show  windows  are  sealed  so  as  not 
to  permit  infiltration  and  since  there  are  only  three  doors  in  this  store  through  which 
infiltration  can  take  place,  it  is  obvious  that  infiltration  of  air  will  be  a  negligible  quan- 
tity. The  volume  of  the  store  is  21,600  cu  ft.  Good  practice  indicates  that  in  a  store 
of  this  character  there  should  be  a  minimum  of  from  ltol%  outside  air  changes  per  hour. 
On  a  basis  of  1}4  air  changes  the  volume  of  outside  air  to  be  ^introduced  would  be  32,400 
cfh.  By  reference  to  Chapter  3  it  will  be  noted  that  the  minimum  ventilation  require- 
ments are  10  cfm  per  person.  On  this  basis  the  ventilation  requirements  would  be 
30,000  cfh.  Since  this  will  produce  approximately  IJi  outside  air  changes  per  hour, 
30,000  cfh  will  be  considered  in  this  application. 

To  determine  load  imposed  by  occupants  it  will  be  found  from  Table  4,  Chapter  3 
that  the  average  person  standing  at  rest  will  dissipate  225  Btu  sensible  heat  and  206 
Btu  latent  heat  per  hour. 

NORMAL  TRANSMISSION  LOAD: 


SURFACE 

DIMENSIONS 

AREA 

SQ  FT 

U 

TEMP.  DIFF. 
DEGP 

BTTJ  PBB 
HOUR 

S  Glass 

S  Wall 
W  Wall 
WDoor 
Roof 
Floor 
N  Partition 

Total 

2(2  ft  6  in.  x  7ft)  + 
2(10  ft  x  6  ft) 
(30  ft  x  12  ft)  -155 
(GO  ft  x  12  ft)  -321 
3  ft  x  7  ft 
60  ft  x  30  ft 
26  ft  x  54  ft 
30  ft  x  12  ft 

155 
205 
399 
21 
1800 
1404 
360 

1.13 
0.33 
0.33 
0.51 
0.26 
0.34 
0.34 

15 
15 
15 
15 
15 
5 
8 

2,627 
1,015 
1,975 
161 
7,020 
2,387 
979 

16,164 

SUN  LOAD: 


SURFACE 

DIMENSIONS 

AREA 

SQ  FT 

.  F 

a 

JOB 
*G 

SHADE 
FACTOR 

BUT  PEE 
HOUR 

SWall 
S  Glass 
W  Glass 

WDoor 
W  Wall 
Roof 

Total 

3(14  ft  x  6  ft)  + 
(8  ft  x  6  ft) 

205 
155 

300 
21 
399 
1800 

0.078 

0.118 
0.078 
0.062 

0.7 

0.7 
0.7 
0.9 

77 
2 

182 
192 
143 
258 

0.28 
0.28 

862 
87 

15,288 
333 
3,113 
25,914 

45,597 

OUTSIDE  AIR  HEAT  GAIN: 

Sensible  heat,  Hs  =  0.24  X  60  d0  Q  (tQ  -  f)  (Formula  4). 
Q  =  50  X  10  =  500  cfm. 

Density  of  air  at  95  F  dry-bulb  and  75  F  wet-bulb  for  a  barometric  pressure  of  29.92  in. 
is  0.07089  Ib  per  cubic  foot  (Table  4,  Chapter  1). 

Dew-point  of  outdoor  air  is  66  F  (psychrometric  chart). 

162 


CHAPTER  8.    COOLING  LOAD 


Partial  pressure  of  vapor  is  0.64378  in.  Hg.  (Pressure  of  saturated  vapor  at  66  F, 
Table  6,  Chapter  1). 


a622 


°-622 


=  a°137  lb  water  vapor  per 


pound  dry  air  (Formula  5  a,  Chapter  1). 
-  —  :  -  n  nlQ-  =  0.986  lb  dry  air  per  pound  outside  air. 

1  plUS  U.Uloi 

do  =  0.07089  X  0.986  =  0.0699  lb  dry  air  per  cubic  foot  outside  air. 

H6  =-  60  X  500  X  0.0699  X  0.24  (95-80)  -  7549  Btu  per  hour. 

Total  heat,  H  =  60  dQ  Q  (h0  -  K)  (Formula  5). 

h0  =  38.46  Btu  per  pound  dry  air  at  75  F  wet-bulb  (Table  6,  Chapter  1). 
h  =  31.51  Btu  per  pound  dry  air  at  67  F  wet-bulb  (Table  6,  Chapter  1). 
H  =  60  X  0.0699  X  500  (38.46  -  31.51)  =  14,574  Btu  per  hour. 

Latent  heat  gain  from  outside  air  =  14,574  —  7549  =  7025  Btu  per  hour. 
PEOPLE  HEAT  GAIN: 

50  X  225  =  11,250  Btu  per  hour,  sensible  heat. 

50  X  206  =  10,300  Btu  per  hour,  latent  heat. 
LIGHT  HEAT  GAIN: 

4200  X  3.413  =  14,335  Btu  per  hour. 
SUMMARY: 


CQMPOHPSNT  OF  LQAI» 

BTU  FBI 

i  HOUB 

Sensible 

Latent 

Normal  Transmission  Load  ..  
Sun  Load 

16,164 
45,597 

Outside  Air  Heat  Gain..  
People  Heat  Gain—  -  -  
Light  Heat  Gain  !_  .,  

7,549 
11,250 
14,335 

7,025 
10,300 

TotaL  -  

94,895 

17,325 

TOTAL  LOAD: 
94,895  +  17,325 


112,220  Btu  per  hour. 


PROBLEMS  IN  PRACTICE 

1  •  The  outdoor  and  indoor  temperatures  are  90  F  and  78  F,  respectively.  What 
is  the  amount  of  heat  transmitted  per  hour  through  a  7  ft  by  4  ft  north  window? 

Ht  =  28  X  1.13  (90-78)  «  380  Btu  per  hour.    (Equation  1,  Chapter  8  and  Table  13  A, 
Chapter  5). 

2  •  a.  If  a  restaurant  has  two  10  gal  gas-heated  coffee  urns,  what  is  the  cooling 
load  due  to  them? 

b.  What  is  the  cooling  load  due  to  four  1350  w  burners  on  an  electric  range? 

a.  2  X  10  X  1000  =  20,000  Btu  per  hour  (Table  10). 

b.  4  X  1350  -  5400  w  -  5.4  kw. 

5.4  X  3413  =  18,430  Btu  per  hour  (Table  10). 

3  •  a.  What  is  the  maximum  heat  transmission  for  a  flat  roof  located  in  Pitts- 
burgh  (latitude  40  deg)  exposed  to  the  sun  with  the  outdoor  and  indoor  tem- 

163 


HEATING  VENTILATING  AIR  CONDITIONING  GUIDE  1938 


perature  95  F  and  80  F,  respectively?    The  roof  is  of  uninsulated  6  in.  concrete 
with  its  underside  exposed,  and  -with  a  black  upper  surface. 

b.  What  time  of  day  will  maximum  cooling  load  due  to  the  roof  exist? 

a.  Ht  +  Hjt  =  [A  U  (t0  -  t)]  +  [A  Fal\  (Formulas  1  and  2). 
U  for  roof  =  0,64  (Table  11,  Wall  4  A,  Chapter  5). 

F  -  0.147  (Fig.  2). 

a  -  0.9  (Table  6). 

/  =  293  (Table  4). 

Ht  +  HR    =  [1  X  0.64  (95-80)]  +  [1  X  0.147  X  0.9  X  293]  «  48.5  Btu  per  square 
foot  per  hour. 

b.  Maximum  sun  intensity  occurs  at  noon  (Table  4).    Maximum  effect  in  cooling  load 
will  occur  at  3  p.m.  (Table  7). 

4  •  a.  What  is  the  maximum  rate  of  heat  delivered  to  a  room  through  a  hare 
window  in  the  west  wall  of  a  building  located  in  New  Orleans  (30  deg  latitude)? 

h.  What  tune  of  day  will  it  occur? 

c.  What  will  maximum  rate  be  if  window  is  protected  by  awning? 

a.  HG  =  AG!G  (Formula  3). 
7G  =  177  (Table  2). 
HG  =  1  X  177  =  177  Btu  per  square  foot  per  hour. 

6.  At  4  p.m.  (Table  2). 

c.  177  X  0.28  =  49.6  Btu  per  square  foot  per  hour  (Table  8). 

5  •  What  is  the  heat  gain  per  cubic  foot  of  outside  air  introduced,  under  the 
following  conditions  if  the  barometric  pressure  is  29.5  in.  Hg.? 

Outdoor  temperatures,  90  F  dry-bulb  and  75  F  wet-bulb. 
Inside  temperatures,  78  F  dry-bulb  and  65  F  wet-bulb. 

Density  of  air  at  90  F  dry-bulb,  75  F  wet-bulb  and  29.5  in  Hg.  is  0.0705  Ib  per  cubic  foot 
(Table  4,  Chapter  1). 

Dew-point  of  outdoor  air  is  68.2  F  (psychrometric  chart). 

Pressure  of  saturated  vapor  at  68.2  F  is  0.6946  in.  Hg.  (Table  6,  Chapter  1). 

W  -  0.622  (-JIT?)  =  0.622  (29  S^QSQ^  )  "  °'°15  lb  water  vaP°r  Per  Poun^  dry 
air  (Formula  oa,  Chapter  1). 

—  0.985  Ib  dry  air  per  pound  outside  air. 


j  —  r- 

d0  =  0.0705  X  0.985  =  0.06944  Ib  dry  air  per  cubic  foot  outside  air. 
Heat  content  outside  dry  air  at  75  F  wet-bulb  =  38.46  Btu  per  pound. 
Heat  content  inside  dry  air  at  65  F  wet-bulb  =  29.96  Btu  per  pound. 
Total  heat,  H  »  0.06944  (38.46  -  29.96)  =  0.59  Btu  per  cubic  foot. 

6  •  A  7  X  4  ft  west  window  is  equipped  with  an  inside  aluminum  finished 
Venetian  blind  which  is  adjusted  to  fully  cover  the  window  when  the  sun  shines. 
The^net  glass  area  is  75  per  cent  of  the  total  area  of  the  window.  What  is  the 
cooling  load  due  to  the  window  at  10  a.m.  and  4  p.m.?  Temperatures  are: 
10  a.m.,  outside  85  F  and  inside  77  F;  4  p.m.,  outside  95  F  and  inside  80  F. 
Latitude  40  deg. 

10  a.m.:  Ht  =  28  X  1.13  (85-77)  =  253  Btu  per  hour  (Equation  1,  and  Table  13A, 
Chapter  5). 

4  p.m.:    28  X  0.75  =  21  sq  ft  net  glass  area. 

HG  «*  21  X  182  X  0.58  =  2217  Btu  per  hour  (Tables  4  and  8). 

164 


Chapter  9 

FUELS  AND  COMBUSTION 

Classification  of  Coal,  Air  for  Combustion,  Draft  Required, 

Combustion  of  Anthracite,  Firing  Bituminous  Coal,  Burning 

Coke,  Hand  Firing,  Classification  and  Use  of  Oil,  Classification 

and  Use  of  Gas 

THE  choice  of  fuel  for  heating  is  a  question  of  economy,  cleanliness, 
fuel  availability,  operation  requirements,  and  control.    The  principal 
fuels  to  be  considered  are  coal,  oil,  and  gas. 

CLASSinCATION  OF  COALS 

The  complex  composition  of  coal  makes  it  difficult  to  classify  it  intc 
clear-cut  types.  Its  chemical  composition  is  some  indication  but  coals 
having  the  same  chemical  analysis  may  have  distinctly  different  burning 
characteristics.  Users  are  mainly  interested  in  the  available  heat  pei 
pound  of  coal,  in  the  handling  and  storing  properties,  and  in  the  burning 
characteristics.  A  description  of  the  relationship  between  the  qualitiei 
of  coals  and  these  characteristics  requires  considerable  space;  a  treatmen 
applicable  to  heating  boilers  is  given  in  U.  S.  Bureau  of  Mines  Bulletin  276 

A  classification  of  coals  is  given  in  Table  1,  and  a  brief  description  of  th< 
kinds  of  fuels  is  given  in  the  following  paragraphs,  but  it  should  b 
recognized  that  there  are  no  distinct  lines  of  demarcation  between  th 
kinds,  and  that  they  graduate  into  each  other: 

Anthracite  is  a  clean,  dense,  hard  coal  which  creates  very  little  dust  in  ^  handling.  ^  '. 
is  comparatively  hard  to  ignite  but  it  burns  freely  when  well  started.  It  is  non-cakin! 
it  burns  uniformly  and  smokelessly  with  a  short  flame,  and  it  requires  little  attention  1 
the  fuel  beds  between  firings.  It  is  capable  of  giving  a  high  efficiency  in  the  commc 
types  of  hand-fired  furnaces.  A  tabulation  of  the  quality  of  the  various  anthraci 
sizes  will  be  found  in  U.  S.  Bureau  of  Mines  Report  of  Investigations  No.  3283. 

Semi-anthracite  has  a  higher  volatile  content  than  anthracite,  it  is  not  as  hard  ax 
ignites  somewhat  more  easily;  otherwise  its  properties  are  similar  to  those  of  anthracit 

Semi-bituminous  coal  is  soft  and  friable,  and  fines  and  dust  are  created  by  handling 
It  ignites  somewhat  slowly  and  burns  with  a  medium  length  of  flame.^  Its  caking  pr 
perties  increase  as  the  volatile  matter  increases,  but  the  coke  formed  is  relatively  wea 
Having  only  half  the  volatile  matter  content  of  the  more  abundant  bituminous  coals 
can  be  burned  with  less  production  of  smoke,  and  it  is  sometimes  called  smokeless  co 

The  term  bituminous  coal  covers  a  large  range  of  coals  and  includes  many  types  havi 
distinctly  different  composition,  properties,  and  burning  characteristics.  The  coals  rat 
from  the  high-grade  bituminous  coals  of  the  East  to  the  poorer  coals  of  the  West.  Th 
caking  properties  range  from  coals  which  completely  melt,  to  those  from  which  1 
volatiles  and  tars  are  distilled  without  change  of  form,  so  that  they  are^  classed  as  n< 
caking  or  free-burning.  Most  bituminous  coals  are  strong  and  non-friable  enough 
permit  of  the  screened  sizes  being  delivered  free  from  fines.  In  general,  they  ign 

165 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

easily  and  burn  freely ;  the  length  of  flame  varies  with  different  coals,  but  it  is  long.  Much 
smoke  and  soot  are  possible  especially  at  low  rates  of  burning. 

Sub-bituminous  coals  occur  in  the  western  states;  they  are  high  in  moisture  when 
mined  and  tend  to  break  up  as  they  dry  or  when  exposed  to  the  weather;  they  are  liable 
to  ignite  spontaneously  when  piled  or  stored.  They  ignite  easily  and  quickly  and  have  a 
medium  length  flame,  are  non-caking  and  free-burning;  the  lumps  tend  to  break  into 
small  pieces  if  poked;  very  little  smoke  and  soot  are  formed. 

Lignite  is  of  woody  structure,  very  high  in  moisture  as  mined,  and  of  low  heating 
value;  it  is  clean  to  handle.  It  has  a  greater  tendency  than  the^sub-bituminous  coals  to 
disintegrate  as  it  dries,  and  it  also  is  more  liable  to  spontaneous  ignition.  Freshly  mined 
lignite,  because  of  its  high  moisture,  ignites  slowly.  It  is  non-caking.  The  char  left  after 
the  moisture  and  volatile  matter  are  driven  off  burns  very  easily,  like  charcoal.  The 
lumps  tend  to  break  up  in  the  fuel  bed  and  pieces  of  char  falling  into  the  ashpit  continue 
to  burn.  Very  little  smoke  or  soot  is  formed. 

Coke  is  produced  by  the  distillation  of  the  volatile  matter  from  coal.  The  type  of 
coke  depends  on  the  coal  or  mixture  of  coals  used,  the  temperatures  and  time  of  distil- 
lation and,  to  some  extent,  on  the  type  of  retort  or  oven;  coke  is  also  produced  as  a 
residue  from  the  destructive  distillation  of  oil. 


TABLE  1.    CLASSIFICATION  OF  COALS  BY  RANK/ 
Legend:  F.C.  =  Fixed  Carbon.    V.M.  =  Volatile  Matter.   Btu  =  British  thermal  units. 


CLASS 

GEOUP 

LIMITS  o?  FECED  CARBON  OR  BTU 
MINERAL-MATTER-FRBZ  BASIS 

REQUISITE  PHYSICAL 
PROPERTIES 

i.  Meta-anthracite  

Dry  F.C.,  98  per  cent  or  more  (Dry 

V.M.,  2  per  cent  or  less) 

I.  Anthracite  

2   Anthracite                  

Dry  F.C.,  92  per  cent  or  more  and  less 
than  98  per  cent  (Dry  V.M.,  8  per 
cent  or  less  and  more  than  2  per  cent) 
Dry  F.C.,  86  per  cent  or  more  and  less 
than  92  per  cent  (Dry  V.M.,  14  per 

Non-agglutinating0 

3  Semi-anthracite 

cent  or  less  and  more  than  8  per  cent) 

1  Low  volatile  bituminous  coal  — 

Dry  F.C.,  77  per  cent  or  more  and  less 

than  86  per  cent  (Dry  V.M.,  23  per 

cent  or  less  and  more  than  14  per 

cent) 

2.  Medium  volatile  bituminous  coal 

Dry  F,C.,  69  per  cent  or  more  and  less 
than  77  per  cent  (Dry  V.M.,  31  per 

cent  or  less  and  more  than  23  per 

I^_  Bituminous0—  ' 

cent) 

3.  High  volatile  A  bituminous  coal. 

Dry  F.C.,  less  than  69  per  cent  (Dry 
V.M.,  more  than  31  per  cent);  and 

moist6  Btu,  14,000*  or  more 

4.  High  volatile  B  bituminous  coal.. 

Moist*  Btu,  13,000  or  more  and  less 

than  14,000* 

5  High  volatile  C  bituminous  coal- 

Moist  Btu,  11,000  or  more  and  less 
than  13,000* 

Either  agglutinating 
or  non-weathering* 

f 

I.  Sub-bituminous  A  coal  

Moist  Btu,  11,000  or  more  and  less 

Both  weathering  and 

| 

than  13,000* 

non-agglutinating 

III.  Sub-bituminous., 

2.  Sub-bituminous  B  oo^-l  .„.,_    ....  , 

Moist  Btu  9500  or  more  and  less 
than  11,000* 

3.  Sub-bituminous  C  coal  

Moist  Btu  8300  or  more  and  less 

than  9500* 

:1   T  lignite 

Moist  Btu  less  than  8300 

Consolidated 

2  "Rro^ra  coal              .  ri 

Moist  Btu  less  than  8300 

Unconsolidated 

•If  agglutinating,  classify  in  low-volatile  group  of  the  bituminous  class. 

*Moist  Btu  refers  to  coal  containing  its  natural  bed  moisture  but  not  including  visible  water  on  the 
surface  of  the  coal. 

•Pending  the  report  of  the  Subcommittee  on  Origin  and  Composition  and  Metbods  of  Analysis,  it  is 
recognized  that  there  may  be  non-caking  varieties  in  each  group  of  the  bituminous  class. 

*Coals  having  69  per  cent  or  more  fixed  carbon  on  tbe  dry,  mineral-matter-free  basis  shall  be  classified 
according  to  fixed  carbon,  regardless  of  Btu. 

•There  are  three  varieties  of  coal  in  the  Higb- volatile  C  bituminous  coal  group,  namely,  Variety  1, 
agglutinating  and  non-weathering;  Variety  2,  agglutinating  and  weathering;  Variety  3,  non-agglutinating 
and  non-weathering. 

/Adapted  from  .4 .S.T.lf.  Standards  on  Coal  and  Coke,  p.  68,  American  Society  for  Testing  Materials, 
Philadelphia,  1934. 

166 


CHAPTER  9.   FUELS  AND  COMBUSTION 


High-temperature  cokes.  Coke  as  usually  available  is  of  the  high-temperature  type, 
and  contains  between  1  and  2  per  cent  volatile  matter.  High-temperature  cokes  are  sub- 
divided into  beehive  coke  of  which  comparatively  little  is  now  sola  for  domestic  use,  by- 
product  coke,  which  covers  the  greater  part  of  the  coke  sold,  and  gas-house  coke.  The 
differences  among _  these  three  cokes  are  relatively  small;  their  denseness  and  hardness 
decrease  and  friability  increases  in  the  order  named.  In  general,  the  lighter  and  more 
friable  cokes  ignite  and  burn  the  more  easily. 

Low-temperature  cokes  are  produced  at  low  coking  temperatures,  and  only  a  portion 
of  the  volatile  matter  is  distilled  off.  Cokes  as  made  by  various  processes  under  develop- 
ment have  contained  from  10  to  15  per  cent  volatile  matter.  In  general,  these  cokes 
ignite  and  burn  more  readily  than  high-temperature  cokes.  The  properties  of  various 
low-temperature  cokes  may  differ  more  than  those  of  the  various  high-temperature  cokes 
because  of  the  differences  in  the  quantities  of  volatile  matter  and  because  some  may  be 
light  and  others  briquetted. 

The  sale  of  petroleum  cokes  for  domestic  furnaces  has  been  small  and  is  generally 
confined  to  the  Middle  West.  They  vary  in  the  amount  of  volatile  matter  they  contain, 
but  all  have  the  common  property  of  a  very  low  ash  content,  which  necessitates  the 
use  of  refractory  pieces  to  protect  the  grates  from  being  burned. 

In  order  to  obtain  perfect  combustion  a  definite  amount  of  air  is  re- 
quired for  each  pound  of  fuel  fired.  A  deficiency  of  air  supply  will  result 
in  combustible  products  passing  to  the  stack  unburned,  An  excess  of  air 
absorbs  heat  from  the  products  of  combustion  and  results  in  a  greater  loss 
of  sensible  heat  to  the  stack. 

Total  Air  Required.  The  theoretical  amount  of  air  required  per  pound 
of  fuel  for  perfect  combustion  is  dependent  upon  the  analysis  of  the  fuel ; 

TABLE  2.    POUNDS  OF  AIR  PER  POUND  OF  FUEL  AS  FIRED 


ANTHRACITE 

Con 

Sma-BrruMiNOTJS 

BlTUHINOTTS 

LlGNTTI 

9.6 

11.2 

11.2 

10.3 

6.2 

however,  for  estimating  purposes  the  theoretical  air  required  for  different 
grades  of  fuel  may  roughly  be  taken  from  Table  2.  An  excess  ^of  about 
50  per  cent  over  the  theoretical  amount  is  considered  good  practice  under 
usual  operating  conditions. 

The  amount  of  excess  air,  based  upon  the  laws  of  combustion,  can  be 
determined  by  its  relation  to  the  percentage  of  CO*  (carbon  dioxide)  in 
the  products  of  combustion.  This  relationship  is  shown  by  the  curves 
(Fig.  1)  for  high  and  low  volatile  coals  and  for  coke.  In  hand-fired  fur- 
naces with  long  periods  between  firings  the  combustion  goes  through  a 
cycle  in  each  period  and  the  quantity  of  excess  air  present  varies. 

Secondary  Air.  The  division  of  the  total  into  primary  and  secondary 
air  necessary  to  produce  the  same  rate  of  burning  and  the  same  excess  air 
depends  on  a  number  of  factors  which  include  size  of  fuel,  depth  of  fuel 
bed,  and  diameter  of  firepot.  The  ratio  of  the  secondary  to  the  primary 
air  increases  with  decrease  in  the  size  of  the  fuel  pieces,  with  increase  in 
the  depth  of  the  fuel  bed,  and  with  increase  in  the  area  of  the  firepot;  the 
ratio  also  increases  with  increase  in  rate  of  burning. 

Size  of  the  fuel  is  a  very  important  factor  in  fixing  the  quantity  of 
secondary  air  required  for  non-caking  coals.  With  caking  coals  it  is  not 

167 


HEATING  VENTILATING  AIR  CONDITIONING  GUIDE  1938 


22 

20 
18 

o 

g  14 


'      I      I 


YV  XjL 


\V\ 


Low-volatile  . 
./bituminous  coa 


J  High  -  volatile  •_ 
'bituminous  coal 


~~20 40   60    80   100   120   140   160 
EXCESS  AIR,  PER  CENT 


FIG.  1*  RELATION  BETWEEN  C03  AND  EXCESS  AIR  IN  GASES  OF  COMBUSTION 

so  important  because  small  pieces  fuse  together  and  form  large  lumps. 
Fortunately  a  smaller  size  fuel  gives  more  resistance  to  air  flow  through 
the  f  uel^  bed  and  thus  automatically  causes  a  larger  draft  above  the  fuel 
bed,  which  draws  in  more  secondary  air  through  the  same  slot  openings. 
In  spite  of  this,  ^a  small  size  fuel  requires  a  larger  opening  of  the  door 
slots;  for  a  certain  size  for  each  fuel  no  slot  opening  is  required,  and  for 
larger  sizes  too  much  excess  air  gets  through  the  fuel  bed. 

It  is  impossible  to  establish  a  single  rule  for  the  correct  slot  opening  for 
all  types  and  sizes  of  fuels  and  for  all  rates  of  burning.  Furthermore,  the 


s 

iflojlw 

/ 

s 

/ 

* 

s 

^ 

/ 

/ 

? 

/ 

' 

±J 

/ 

/ 

/ 

\ 

Y 

.> 

/ 

/ 

in 

/ 

w 

,<< 

7 

/ 

/ 

/ 

/ 

/ 

>v 

/ 

/ 

s 

/ 

* 

/ 

/ 

Sfc 

ttdc 

*ed 

f 

/ 

EATEOFBim 

NING,  POUNDS  PER  SQ.  FT.  PBH  HR. 

From  U.  S,  Bureau  of  Mi 

nes. 

FIG.  2.    RELATIVE  AMOUNT  OF  FIRE  DOOR  SLOT  OPENING  REQUIRED  IN  A  GIVEN 
FURNACE  TO  GIVE  EQUALLY  GOOD  COMBUSTION  FOR  HIGH  TEMPERATURE 
COKE  OF  VARIOUS  SIZES  WHEN  BURNED  AT  VARIOUS  RATES 

168 


CHAPTER  9.   FUELS  AND  COMBUSTION 


size  of  slot  opening  is  dependent  on  whether  the  ashpit  damper  is  open 
or  closed.  It  is  better  to  have  too  much  than  too  little  secondary  air;  the 
opening  is  too  small  if  there  is  a  puff  of  flame  when  the  firing  door  is  opened. 
Fig.  2,  taken  from  the  17.  S.  Bureau  of  Mines  Report  of  Investigations 
No.  2980,  shows  the  relationship  of  the  slot  opening,  for  a  domestic  fur- 
nace, to  the  size  of  coke  and  the  rate  of  burning;  these  openings  are  with 
the  ashpit  ^damper  wide  open,  and  would  be  less  if  the  available  draft 
permits  of  its  being  partly  closed.  The  same  openings  are  satisfactory  for 
anthracite. 

Bituminous  coals  require  a  large  amount  of  secondary  air  during  the 
period  subsequent  to  a  firing  in  order  to  consume  the  gases  and  to  reduce 
the  smoke.  The  smoke  produced  is  a  good  indicator,  and  that  opening  is 
best  which  reduces  the  smoke  to  a  minimum.  Too  much  secondary  air 
will  cool  the  gases  below  the  ignition  point,  and  prove  harmful  instead  of 
beneficial  The  following  suggestions  will  be  helpful: 

1.  In  cold  weather,  with  high  combustion  rates,  the  secondary  air  damper  should  be 
half  open  all  the  time. 

2.  In  very  mild  weather,  with  a  very  low  combustion  rate,  the  secondary  air  damper 
should  be  closed  all  the  time. 

3.  For  temperatures  between  very  mild  and  very  cold,  the  secondary  air  damper 
should  be  in  an  intermediate  position. 

4.  For  ordinary  house  operation,  secondary  air  is  needed  after  each  firing  for  about 
one  hour. 

Draft  Requirements 

The  draft  required  to  effect  a  given  rate  of  burning  the  fuel  as  measured 
at  the  smokehood  is  dependent  on  the  following  factors: 

1.  Kind  and  size  of  fuel. 

2.  Combustion  rate  per  square  foot  of  grate  area  per  hour. 

3.  Thickness  of  fuel  bed. 

4.  Type  and  amount  of  ash  and  clinker  accumulation. 

5.  Amount  of  excess  air  present  in  the  gases. 

6.  Resistance  offered  by  the  boiler  passes  to  the  flow  of  the  gases. 

7.  Accumulation  of  soot  in  the  passes. 

Insufficient  draft  will  necessitate  additional  manipulation  of  the  fuel 
bed  and  more  frequent  cleanings  to  keep  its  resistance  down.  Insufficient 
draft  also  restricts  the  control  by  adjustment  of  the  dampers. 

The  quantity  of  excess  air  present  has  a  marked  effect  on  the  draft 
required  to  produce  a  given  rate  of  burning,  and  it  is  often  possible  to 
produce  a  higher  rate  by  increasing  the  thickness  of  the  fuel  bed. 

Combustion  of  Anthracite1 

An  anthracite  fire  should  never  be  poked,  as  this  serves  to  bring  ash  to 
the  surface  of  the  fuel  bed  where  it  melts  into  clinker. 

Egg  size  is  suitable  for  large  firepots  (grates  24  in.  and  over)  if  the  fuel 
can  be  fired  at  least  16  in.  deep.  The  air  spaces  between  the  pieces  of  coal 
are  large,  and  for  best  results  this  coal  should  be  fired  deeply. 


lSee  reports  published  by  Anthracite  Industries  Laboratory,  Primes,  Pennsylvania. 

169 


HEATING  VENTILATING  AIR  CONDITIONING  GUIDE  1938 


Stove  size  coal  is  the  proper  size  of  anthracite  for  many  boilers  and 
furnaces  used  for  heating  buildings.  It  burns  well  on  grates  at  least  16  in. 
in  diameter  and  12  in.  deep.  The  only  instructions  needed  for  burning 
this  type  of  fuel  are  that  the  grate  should  be  shaken  daily,  the  fire  should 
never  be  poked  or  disturbed,  and  the  fuel  should  be  fired  deeply  and 
uniformly. 

Chestnut  size  coal  is  in  demand  for  firepots  up  to  20  in.  in  diameter,  with 
a  depth  of  from  10  to  15  in. 

Pea  size  coal  is  often  an  economical  fuel  to  burn.  It  is  relatively  low 
in  price.  When  fired  carefully,  pea  coal  can  be  burned  on  standard  grates. 
It  is  well  to  have  a  small  amount  of  a  larger  fuel  on  hand  when  building 
new  fires,  or  when  filling  holes  in  the  fuel  bed.  Care  should  be  taken  to 
shake  the  grates  only  until  the  first  bright  coals  begin  to  fall  through  the 
grates.  The  fuel  bed,  after  a  new  fire  has  been  built,  should  be  increased 
in  thickness  by  the  addition  of  small  charges  until  it  is  at  least  level  with 
the  sill  of  the  fire  door.  This  keeps  a  bed  of  ignited  coal  in  readiness 
against  the  time  when  a  sudden  demand  for  heat  shall  be  made  on  the 
heater.  A  very  satisfactory  method  of  firing  pea  coal  consists  of  drawing 
the  red  coals  toward  the  front  end  and  piling  fresh  fuel  toward  the  back 
of  the  fire-box. 

Pea  size  coal  requires  a  strong  draft  and  therefore  the  best  results 
generally  will  be  obtained  by  keeping  the  choke  damper  open,  the  cold- 
air  check  closed,  and  by  controlling  the  fire  with  the  air-inlet  damper  only. 
Pea  size  can^also  be  fired  in  layers  with  stove  or  egg  size  anthracite  and 
its  use  in  this  manner  will  reduce  the  fuel  costs  and  attention  required. 
^  Buckwheat  size  coal  for  best  results  requires  more  attention  than  pea 
size  coal,  and  in  addition  the  smaller  size  of  the  fuel  makes  it  more  difficult 
to  burn  on  ordinary  grates.  Greater  care  must  be  taken  in  shaking  the 
grates  than  with  pea  coal  on  account  of  the  danger  of  the  fuel  falling 
through  the  grate.  In  house  heating  furnaces  the  coal  should  be  fired 
lightly  and^more  frequently  than  pea  coal.  When  banking  a  buckwheat 
coal  fire  it  is  advisable  after  coaling  to  expose  a  small  spot  of  hot  fire  by 
putting  a  poker  down  through  the  bed  of  fresh  coal.  This  will  serve  to 
ignite  ^the  gas  that  will  be  distilled  from  the  fresh  coal  and  prevent  an 
explosion  of  gas  within  the  firepot,  which  in  some  cases  depending  upon  the 
thickness  of  the  bed  of  fresh  coal  is  severe  enough  to  blow  open  the  doors 
and  dampers  of  the  furnace.  A  good  draft  is  required  and  consequently 
the  fire  is  best  controlled  by  the  air-inlet  damper  only.  Where  frequent 
attention  can  be  given  and  care  exercised  in  manipulation  of  the  grates  this 
fuel  can  be  burned  satisfactorily  without  the  aid  of  any  special  equipment. 
In  general  it  will  be  found  more  satisfactory  with  buckwheat  coal  to 
maintain  a  uniform  heat  output  and  consequently  to  keep  the  system 
warm  all  the  time,  rather  than  to  allow  the  system  to  cool  off  at  times 
and  then  to  attempt  to  burn  the  fuel  at  a  high  rate  while  warming  up.  A 
uniform  low  fire  will  minimize  the  clinker  formation  and  keep  the  clinker 
in  an  easily  broken  up  condition  so  that  it  readily  can  be  shaken  through 
the  grate. 

Forced  draft  and  small  mesh  grates  are  frequently  used  for  burning 
buckwheat  anthracite.  For  best  results  and  a  higher  degree  of  con- 
venience, domestic  stokers  are  used. 

170 


CHAPTER  9.   FUELS  AND  COMBUSTION 


No.  2  buckwheat  anthracite,  or  rice  size,  is  used  only  in  domestic 
stokers.  No.  3  buckwheat  anthracite,  or  barley,  has  no  application  in 
domestic  heating. 

Firing  Bituminous  Coal 

Bituminous  coal  should  never  be  fired  over  the  entire  fuel  bed  at  one 
time.  A  portion  of  the  glowing  fuel  should  always  be  left  exposed  to 
ignite  the  gases  leaving  the  fresh  charge. 

Air  should  be  admitted  over  the  fire  through  a  special  secondary  air 
device,  or  through  a  slide  in  the  fire  door  or  by  opening  the  fire  door 
slightly.  If  the  quantity  of  air  admitted  is  too  great  the  gases  will  be 
cooled  below  the  ignition  temperature  and  will  fail  to  burn.  The  fireman 
can  judge  the  quantity  of  air  to  admit  by  noting  when  the  air  supplied 
is  just  sufficient  to  make  the  gases  burn  rapidly  and  smokelessly  above  the 
fuel  bed. 

The  red  fuel  in  the  firebox,  before  firing,  excepting  only  a  shallow  layer 
of  coke  on  the  grate,  should  be  pushed  to  one  side  or  forward  or  back- 
ward to  form  a  hollow  in  which  to  throw  the  fresh  fuel.  Some  manu- 
facturers recommend  that  all  red  fuel  be  pushed  to  the  rear  of  the  firebox 
and  that  the  fresh  fuel  be  fired  directly  on  the  grate  and  allowed  to  ignite 
from  the  top.  The  object  of  this  is  to  reduce  the  early  rapid  distillation 
of  gases  and  to  reduce  the  quantity  of  secondary  air  required  for  smoke- 
less combustion. 

It  is  well  to  have  the  bright  fuel  in  the  firebox  so  placed  that  the  gases 
from  the  freshly  fired  fuel,  mixed  with  the  air  over  the  fuel  bed,  pass 
over  the  bed  of  bright  fuel  on  the  way  to  the  flues.  The  bed  of  bright 
fuel  then  supplies  the  heat  to  raise  the  mixture  of  air  and  gas  to  the 
ignition  temperature,  thereby  causing  the  gaseous  matter  to  burn  and 
preventing  the  formation  of  smoke. 

The  fuel  bed  should  be  carried  as  deep  as  the  size  of  fuel  and  the 
available  draft  permit,  in  order  to  have  as  much  coked  fuel  as  possible 
for  pushing  to  the  rear  of  the  firebox  at  the  time  of  firing.  A  deep  fuel 
bed  allows  the  longest  firing  intervals. 

If  the  coal  is  of  the  caking  kind  the  fresh  charge  will  fuse  into  one 
solid  mass  which  can  be  broken  up  with  the  stoking  bar  and  leveled  from 
20  min  to  one  hour  after  firing,  depending  on  the  temperature  of  the 
firebox.  Care  should  be  exercised  when  stoking  not  to  bring  the  bar  up 
to  the  surface  of  the  fuel  as  this  will  tend  to  bring  ash  into  the  high 
temperature  zone  at  the  top  of  the  fire,  where  it  will  melt  and  form 
clinker.  The  stoking  bar  should  be  kept  as  near  the  grate  as  possible 
and  should  be  raised  only  enough  to  break  up  the  fuel.  With  fuels  requir- 
ing stoking  it  may  not  be  necessary  to  shake  the  grates,  as  the  ash  is 
usually  dislodged  during  stoking. 

The  output  obtained  from  any  heater  with  bituminous  coal  will  usually 
exceed  that  obtainable  with  anthracite,  since  soft  coal  burns  more  rapidly 
than  hard  coal  and  with  less  draft.  Soft  coal,  however,  will  require 
frequent  attention  to  the  fuel  bed,  because  it  burns  unevenly,  even 
though  the  fuel  bed  may  be  level,  forming  holes  in  the  fire  which  admit 
too  much  air,  chilling  the  gases  over  the  fuel  bed  and  reducing  the 
available  draft. 

171 


HEATING  VENTILATING  AIR  CONDITIONING   GUIDE  1938 

Semi-bituminous  coal  is  fired  as  bituminous  coal,  and  because  of  its 
caking  characteristics  it  requires  practically  the  same  attention.  The 
Pocahontas  Operators  Association  recommends  the  central  cone  method  of 
firing,  in  which  the  coal  is  heaped  on  to  the  center  of  the  bed  forming  a 
cone  the  top  of  which  should  be  level  with  the  middle  of  the  firing  door. 
This  allows  the  larger  lumps  to  fall  to  the  sides,  and  the  fines  to  remain  in 
the  center  and  be  coked.  The  poking  should  be  limited  to  breaking  down 
the  coke  without  stirring,  and  to  gently  rocking  the  grates.  It  is  recom- 
mended that  the  slides  in  the  firing  door  be  kept  closed,  as  the  thinner  fuel 
bed  around  the  sides  allows  enough  air  to  get  through. 

Burning  Coke 

Coke  is  a  very  desirable  fuel  and  usually  will  give  satisfaction  as  soon 
as  the  user  learns  how  to  control  the  fire.  Coke  ignites  and  burns  very 
rapidly  with  less  draft  than  anthracite  coal.  In  order  to  control  the  air 
admitted  to  the  fuel  it  is  very  important  that  all  openings  or  leaks  into 
the  ashpit  be  closed  tightly.  A  coke  fire  responds  more  rapidly  than  an 
anthracite  fire  to  the  opening  of  the  dampers.  This  is  an  advantage  in 
warming  up  the  system,  but  it  also  makes  it  necessary  to  watch  the 
dampers  more  closely  in  order  to  prevent  the  fire  from  burning  too  rapidly. 
A  deep  fuel  bed  always  should  be  maintained  when  burning  coke.  The 
grates  should  be  shaken  only  slightly  in  mild  weather  and  should  be 
shaken  only  until  the  first  red  particles  drop  from  the  grates  in  cold 
weather.  Since  coke  weighs  only  about  half  as  much  as  anthracite  per 
cubic  foot  only  about  half  as  much  can  be  put  in  the  firepot,  so  it  will  be 
necessary  to  fire  oftener.  The  best  size  of  coke  for  general  use,  for  small 
firepots  where  the  fuel  depth  is  not  over  20  in.,  is  that  which  passes  over 
a  1  in.  screen  and  through  a  1 J^  in.  screen.  For  large  firepots  where  the 
fuel  can  be  fired  over  20  in.  deep,  coke  which  passes  over  a  1  in.  screen  and 
through  a  3  in.  screen  can  be  used,  but  a  coke  of  uniform  size  is  always 
more  satisfactory.  Large  sizes  of  coke  should  be  either  mixed  with  fine 
sizes  or  broken  up  before  using. 

Dustless  Coal 

The  practice  of  treating  the  more  friable  coals  to  allay  the  dust  they 
create  is  increasing.  The  coal  is  sprayed  with  a  solution  of  calcium 
chloride  or  a  mixture  of  calcium  and  magnesium  chlorides.  Both  these 
salts  are  very  hygroscopic  and  their  moisture  under  normal  atmospheric 
conditions  keeps  the  surface  of  the  coal  damp,  thus  reducing  the  dust 
during  delivery  and  in  the  cellar,  and  obviating  the  necessity  of  sprinkling 
the  coal  in  the  bin. 

The  coal  is  sometimes  treated  at  the  mine,  but  more  usually  by  the 
local  distributor  just  before  delivery.  The  solution  is  sprayed  under  high 
pressure,  using  from  2  to  4  gal  or  from  5  to  10  Ib  of  the  salt  per  ton  of 
coal,  depending  on  its  friability  and  size. 

Pulverized  Coal 

Installations  of  pulverized  coal  burning  plants  in  heating  boilers  are  of 
the  unit  type,  in  which  the  pulverized  coal  is  delivered  into  the  furnace 
immediately  after  grinding,  together  with  the  proper  amount  of  preheated 

172 


CHAPTER  9.   FUELS  AND  COMBUSTION 


air.    With  ^this  apparatus,  where  the  necessary  furnace  volume  is  ob- 
tainable, high  efficiencies  can  be  obtained. 

A  150-hp  boiler  has  generally  been  considered  the  smallest  size  for 
which  pulverized  fuel  is  feasible.  Complications  are  introduced  if  an 
installation  with  a  single  boiler  has  to  take  care  of  very  light  loads. 

Hand  Firing 

Hand  firing  is  the  oldest  and  the  most  widely  used  method  of  burning 
coal  for  heating  purposes.  To  keep  the  fuel  bed  in  proper  condition  where 
hand  firing  is  used,  the  following  general  rules  should  be  observed: 

1.  Remove  ash  from  fuel  bed  by  shaking  the  grates  whenever  fresh  fuel  is  fired.  This 
removes  ash  from  the  fire,  enables  the  air  to  reach  the  fuel,  and  does  away  with  the  for- 
mation of  clinker  which  is  melted  ash. 

2.  Supply  the  boiler  with  a  deep  bed  of  fuel.    Nothing  is  gained  by  attempting  to 
fire  a  small  amount  of  fuel.   A  deep  bed  of  fuel  secures  the  most  economical  results. 

3.  Remove  ash  from  ashpit  at  least  once  daily.    Never  allow  ash  to  accumulate  up 
to  the  grates.    If  the  ash  prevents  the  air  from  passing  through,  the  grate  bars  will 
burn  out  and  much  clinker  trouble  will  be  experienced. 

The  principal  requirements  for  a  hand-fired  furnace  are  that  it  shall  have 
enough  grate  area  and  correctly  proportioned  combustion  space.  The 
amount  of  grate  area  required  is  dependent  upon  the  desired  combustion 
rate. 

The  furnace  volume  is  influenced  by  the  kind  of  coal  used.  Bituminous 
coals,  on  account  of  their  long-flaming  characteristic,  require  more  space 
in  which  to  burn  the  gases  of  combustion  completely  than  do  the  coals 
low  in  volatile  matter.  For  burning  high  volatile  coals  provision  should 
be  made  for  mixing  the  combustible  gases  thoroughly  so  that  com- 
bustion is  complete  before  the  gases  come  in  contact  with  the  relatively 
cool  heating  surfaces.  An  abrupt  change  in  the  direction  of  flow  tends  to 
mix  the  gases  of  combustion  more  thoroughly.  Anthracite  requires 
practically  no  combustion  space. 

CLASSIHCATION  OF  OILS 

Uniform  oil  specifications  were  prepared  in  1929  by  the  American  Oil 
Burner  Association,  in  cooperation  with  the  American  Petroleum  Institute, 
the  U.  S.  Bureau  of  Standards,  the  American  Society  for  Testing  Materials 
and  other  interested  organizations.  Oil  fuels  were  classified  into  six 
groups,  as  indicated  by  Table  3.  When  these  specifications  were  prepared, 
it  was  generally  accepted  that  the  first  three  grades  were  adapted  to 
domestic  use,  while  the  last  three  were  suitable  only  for  commercial  and 
industrial  burners. 

^  Today  domestic -installations  may  use  No.  4  oil  of  the  so-called  heavy 
oil  group,  when  and  if  said  oil  very  closely  follows  the  specifications  of 
No.  3.  Up-to-date  listing  by  the  Underwriter's  Laboratories  should  be 
referred  to  before  a  No.  4  grade  of  fuel  is  used  which  merely  meets 
Commercial  Standards  CS  12-35. 

Since  the  specifications  as  originally  drawn  provide  for  maximum  limits 
only  for  the  several  grades,  this  differentiation  has  not  proved  stable. 
Realizing  how  unsatisfactory  it  is  to  have  specifications  which  permit  the 

173 


HEATING  VENTILATING  AIR  CONDITIONING  GUIDE  1938 


TABLE  3.    COMMERCIAL  STANDARD  FUEL  OIL  SPECIFICATIONS* 
A.    Detailed  Requirements  for  Domestic  Fuel  Oils* 


GRADE  OF  OIL 

APPROX. 
Bxu 

PER 

GAL." 

FLASH  POINT 

WATER 

AND 

SEDIMENT, 
MAXIMUM 

CARBON 

RESIDUE 
MAXIMUM 

DISTILLATION 
TEST 

VISCOSITY 
MAXIMUM 

Min.      Max. 

Max.      1      Min. 

No.  1 
Domestic 
Fuel  Oil 
A  light  distillate 
oil   for    use   in 
burners   requir- 
ing a  high  grade 
fuel. 

139,000 

100  F     150  F 
or  legal 

0.05% 

0.02% 

10%  point 
420  F 

End  point 
600  F 

No.  2 
Domestic 
Fuel  Oil 
A  medium  distil- 
late oil  for  use 
in    burners    re- 
quiring  a   high 
grade  fuel. 

141,000 

125  F     190  F 
or  legal 

0.05% 

0.05% 

10%  point 

90%  point 
620  F 

End  point 
600  F 

No.  3 
Domestic 
Fuel  Oil 
A    distillate    fuel 
oil    for    use   in 
burners  where  a 
low  viscosity  oil 
is  required. 

143400 

150  F  i  200  F 
or  legal' 

0.1% 

0.15% 

90%  point 
620  F 

Saybolt 
Universal 
at  100  F 
70  seconds 

•Adapted  from  "Fuel  Oils,"  p.  2,  U.  S,  Department  of  Commerce,  Bureau  of  Standards,  Commercial 
Standard  CS18-S5,  Washington,  1935. 

&POUT  Point  Maximum  is  15  F.  Lower  or  higher  pour  points  may  be  specified  whenever  required  by 
conditions  of  storage  and  use.  However,  these  specifications  shall  not  require  a  pour  point  less  than  0  F 
under  any  conditions. 

"Government  specifications  do  not  give  Btu  per  gallon,  but  they  are  noted  here  for  information  only. 


B.    Detailed  Requirements  for  Industrial  Fuel  Oils* 


GRADE  OF  On. 

APPROX. 
BTU 

PER 

GAL.« 

FLASH  POINT, 

WATER 

AND 

SEDIMENT, 
MAXIMUM 

ASH 
MAXIMUM 

VISCOSITY, 

MAXIMUM 

Min. 

Max. 

No.  4. 
Industrial  Fuel  Oil 

An  oil  known  to  the  trade  as  a  light  fuel 
oil  for  use  in  burners  where  a  low  vis- 
cosity industrial  fuel  oil  is  required. 

144,500 

150  F 

See 

Note* 

1-0% 

0.1% 

Saybolt 
Universal 
at  100  F 
500  seconds 

No.  5 

Industrial  Fuel  Oil 

Same  as  Federal  Specifications  Board 
specification  for  bunker  oil  "B"  for 
burners  adapted  to  the  use  of  indus- 
trial fuel  oil  of  medium  viscosity. 

146,000 

150  F 

1.0% 

0.15% 

Saybolt 
Furol 
at  122  F 
100  seconds 

No.  6 
Industrial  Fuel  Oil 

Same  as  Federal  Specifications  Board 
specification  for  bunker  oil  "C"  for 
burners  adapted  to  oil  of  high  viscosity 

150,000 

150  F 

2.0% 

Saybolt 
Furol 
at  122  F 
300  seconds 

«*Pour  point  may  be  specified  whenever  required  by  conditions  of  storage  and  use.  However,  these 
specifications  shall  not  require  a  pour  point  less  than  15  F  under  any  conditions. 

•Whenever  required,  as  for  example  in  burners  with  automatic  ignition,  a  maximum  flash  point  may 
be  specified.  However,  these  specifications  shall  not  require  a  flash  point  less  than  250  F  under  any  con- 
ditions. 

174 


CHAPTER  9.    FUELS  AND  COMBUSTION 


substitution  of  one  grade  for  another,  the  U.  5.  Bureau  of  Standards  in 
cooperation  with  the  American  Society  for  Testing  Materials  is  figuring 
on  a  new  set  of  specifications  providing  for  definite  limits  for  each  grade. 
When  these  specifications  are  adopted,  it  is  expected  that  the  National 
Board  of  Fire  Underwriters  will  retest  all  burners  using  oils  of  the  maximum 
specifications  for  the  grade  so  that  if  a  burner  is  approved  for  a  certain 
grade  it  will  burn  any  oil  meeting  the  specifications  for  that  particular 
grade. 

Several  burners  adapted  to  industrial  use  have  recently  been  listed  for 
automatic  operation  with  No.  5  oil.  Usually  oils  No.  5  or  6  require 
preheating  for  proper  operation,  but  where  conditions  are  favorable,  No. 
5  can  be  used  without  the  equipment  that  this  entails. 

There  are  two  reasons  for  the  trend  to  lower  grades  of  oil.  While  the 
lighter ^oils  contain  slightly  more  heat  units  per  pound,  the  weight  per 
gallon  increases  more  rapidly  than  the  decrease  in  heat  units  per  pound, 
and  oil  is  bought  by  the  gallon.  As  a  consequence,  while  a  No.  1  oil  may 
contain  139,000  Btu  per  gallon,  oil  No.  5  may  test  146,000  Btu  per  gallon, 
or  6  per  cent  more.  Usually  there  is  a  differential  of  3  to  4  cents  between 
the  No.  1  and  No.  5  oils,  so  that  the  economy  of  buying  the  heavier  fuels 
is  apparent;  there  remains  the  economic  utilization  of  the  heat  content  of 
the  heavier  oils. 

The  cost  of  oil  fuel  is  dependent  also  upon  the  amount  that  can  be 
delivered  at  one  time,  and  the  method  of  delivery.  Common  practice  has 
split  the  tank  of  the  truck  delivering  oils  for  domestic  use  into  compart- 
ments of  150  to  500-gal  capacity,  and  these  unit  dumps  are  made  the  basis 
of  price.  Where  a  truck  can  be  connected  to  a  storage-tank  fill  and 
quickly  discharge  its  oil  by  pump,  the  price  obviously  can  be  less  than 
where  a  smaller  quantity  must  be  drawn  off  in  5-gal  cans  and  poured. 
For  similar  reasons  an  installation  that  can  be  supplied  from  a  tank  car 
on  a  siding  provides  for  a  lower  unit  fuel  cost  than  one  where  the  oil 
must  be  trucked,  even  in  the  large  trucks  holding  2,000  gal  or  more  that 
are  used  for  distributing  the  heavier  oils. 

GAS  CLASSIFICATION 

Gas  is  broadly  classified  as  being  either  natural  or  manufactured. 
Natural  gas  is  a  mechanical  mixture  of  several  combustible  and  inert 
gases  rather  than  a  chemical  compound.  Manufactured  gas  as  dis- 
tributed is  usually  a  combination  of  certain  proportions  of  gases  produced 
by  two  or  more  processes,  and  is  often  designated  as  city  gas. 

When  gas  is  burned  a  large  amount  of  water  vapor  is  produced  as  one 
of  the  products  of  combustion.  This  ordinarily  escapes  up  the  chimney, 
carrying  away  with  it  a  certain  amount  of  heat.  However,  when  the  heat 
value  of  gas  is  determined  in  an  ordinary  calorimeter,  this  water  vapor 
is  condensed  and  the  latent  heat  of  vaporization  that  is  given  up  during 
the  condensation  is  reported  as  a  portion  of  the  heat  value  of  the  gas. 
The  heat  value  so  determined  is  termed  the  gross  or  higher  heat  value  and 
this  is  what  is  ordinarily  meant  when  the  heat  value  of  gas  is  specified. 
The  heat  that  is  reclaimed  by  the  condensation  of  the  water  vapor 
amounts  to  about  10  per  cent  of  the  total  heat  value.  It  is  impractical 
to  utilize  the  entire  higher  heat  value  of  the  gas  in  any  house-heating 

175 


HEATING  VENTILATING  AIR  CONDITIONING  GUIDE  1938 


appliance,  because  to  do  so  it  would  be  necessary  to  cool  the  products  of 
combustion  down  below  their  dew  point,  which  is  ordinarily  in  the 
neighborhood  of  130  F. 

The  actual  dew  point  in  the  chimney  is  different  from  the  theoretical 
value  because  excess  air  is  admitted  not  only  at  the  burner  but  also  at  the 
backdraft  diverter  which  lowers  the  dew  point. 

Natural  gas  is  the  richest  of  the  gases  and  contains  from  80  to  95 
per  cent  methane,  with  small  percentages  of  the  other  combustible 
hydrocarbons.  In  addition,  it  contains  from  0.5  to  5.0  per  cent  of  CO*, 
and  from  1  to  12  or  14  per  cent  of  nitrogen.  The  heat  value  varies  from 
700  to  1500  Btu  per  cubic  foot,  the  majority  of  natural  gases  averaging 
about  1000  Btu  per  cubic  foot.  Table  4  shows  typical  values  for  the 
four  main  oil  fields,  although  values  from  any  one  field  vary  materially. 

Table  4  also  gives  the  calorific  values  of  the  more  common  types  of 
manufactured  gas.  Most  states  have  legislation  which  controls  the  distri- 
bution of  gas  and  fixes  a  minimum  limit  to  its  heat  content.  The  gross 
or  higher  calorific  value  usually  ranges  between  520  and  545  Btu  per  cubic 
foot,  with  an  average  of  535.  A  given  heat  value  may  be  maintained  and 
yet  leave  considerable  latitude  in  the  composition  of  the  gas  so  that  as 
distributed  the  composition  is  not  necessarily  the  same  in  different  dis- 

TABLE  4.   REPRESENTATIVE  PROPERTIES  OF  GASEOUS  FUELS, 
BASED  ON  GAS  AT  60  F  AND  30  IN.  HG. 


GAS 

BnjMBCuFr 

SPECIFIC 
GBATHT, 
Am  - 
1.00 

Ant  RxQtnBXD 
FOE  COMBUS- 
TION, 
(CuFr) 

PRODUCTS  or  COMBUSTION 

THEOBBTZCAL 
FLAME   TEM- 

PEBATUHB, 

(DEO  FAHB) 

TTigh 

(Gross) 

Low 
(Net) 

Cubic  Feet 

ULTI- 
MATE 

GO* 

Dry 
Basis 

COt 

H0 

Total 
with 

N* 

Natural  gas  — 
California 

1200 

1087 

0.67 

11.26 

1.24 

2.24 

12.4 

12.2 

3610 

Natural  gas  — 
Mid-Conti- 
nental 

967 

873 

0.57 

9.17 

0.97 

1.92 

10.2 

11.7 

3580 

Natural  gas  — 
Ohio 

1130 

1025 

0.65 

10.70 

1.17 

2.16 

11.8 

12.1 

3600 

Natural  gas  — 
Pennsylvania 

1232 

1120 

0.71 

11.70 

1.30 

2.29 

12.9 

12.3 

3620 

Retort  coal  gas 

575 

510 

0.42 

5.00 

0.50 

1.21 

5.7 

11.2 

3665 

Coke  oven  gas 

588 

521 

0.42 

5.19 

0.51 

1.25 

5.9 

11.0 

3660 

Carburetted 
water  gas 

536 

496 

0.65 

4.37 

0.74 

0.75 

5.0 

17.2 

3815 

Blue  water  gas 

308 

281 

0.53 

2.26 

0.46 

0.51 

2.8 

22.3 

3800 

Anthracite  pro- 
ducer gas 

134 

124 

0.85 

1.05 

0.33 

0.19 

1.9 

19.0 

3000 

Bituminous 
producer  gas 

150 

140 

0.86 

1.24 

0.35 

0.19 

2.0 

19.0 

3160 

Oil  gas 

575 

510 

0.35 

4.91 

0.47 

1.21 

5.6 

10.7 

3725 

176 


CHAPTER  9.   FUELS  AND  COMBUSTION 


tricts,  nor  at  successive  times  in  the  same  district.  There  are  limits  to  the 
variation  allowable,  because  the  specific  gravity  of  the  gas  depends  on  its 
composition,  and  too  great  a  change  in  the  specific  gravity  necessitates  a 
change  in  the  adjustment  of  the  burners  of  small  appliances. 

Table  4  shows  that  a  large  proportion  of  the  products  of  combustion 
when  gas  is  burned  may  consist  of  water  vapor,  and  that  the  greater  the 
proportion  of  water  vapor,  the  lower  the  maximum  attainable  C0$  by  gas 
analysis.  The  table  also  shows  that  a  low  calorific  value  does  not  neces- 
sarily mean  a  low  flame  temperature  since,  for  example,  natural  gas  has  a 
theoretical  flame  temperature  of  3600  F  and  blue  water  gas  of  3800  F, 
although  it  has  a  calorific  value  less  than  one  third  that  of  natural  gas. 

The  quantity  of  air  given  in  Table  4  is  that  required  for  theoretical 
combustion,  but  with  a  properly  designed  and  installed  burner  the  excess 
air  can  be  kept  low.  The  division  of  the  air  into  primary  and  secondary 
is  a  matter  of  burner  design  and  the  pressure  of  gas  available,  and  also  of 
the  type  of  flame  desired. 

PROBLEMS  IN  PRACTICE 

1  •  Differentiate  between  the  general  characteristics  of  hard  and  soft  coals* 

Hard  coals  contain  fixed  carbon  in  large  proportions  and  in  addition  more  ash  is  present 
especially  in  the  smaller  sizes.  Soft  coals  have  an  increasing  percentage  of  carbon  in 
combination  with  hydrogen  which  is  volatile  and  will  distill  off  under  high  temperature, 
producing  smoke. 

2  •  Name  several  important  properties  of  coal  from  a  utilization  standpoint. 

a.  Caking  tendency,  whether  none,  weak,  or  strong. 

b.  Quantity  of  volatile  matter. 

c.  Friability. 

d.  Fusibility  of  the  ash. 

3  •  What  are  the  main  data  commonly  available  that  fix  the  qualities  of  coal, 
and  do  these  tell  the  whole  story? 

a.  Calorific  value,  Btu  per  pound. 

b.  Proximate  analysis  giving  percentages  of  moisture,  volatile  matter,  fixed  carbon,  ash, 
and  sulphur. 

c.  Temperature  at  which  the  ash  softens. 

d.  Screen  sizes. 

Other  important  qualities  not  usually  given  are  the  friability  of  the  coal,  its  caking 
tendency,  and  the  qualities  of  the  volatile  matter.  The  percentage  of  ash  and  its  fusion 
temperature  do  not  tell  how  the  ash  is  distributed  or  how  much  of  it  is  less  fusible  lumps 
of  slate  or  shale. 

4  •  Are  there  available  complete  and  sufficient  data  on  gas  and  oils  to  fix  their 
burning  properties  and  furnace  requirements? 

Yes.  Because  gas  and  oils  are  of  simple  and  uniform  composition,  data  are  available  to 
fix  their  burning  properties  and  furnace  requirements,  but  the  ability  to  control  their 
combustion  is  somewhat  less  determinable. 

5  •  What  effect  does  moisture  in  fuels  have  on  their  efficiency? 

With  any  solid  fuel,  latent  and  sensible  heat  are  lost  at  the  stack  when  moisture  is  dried 
out  of  the  fuel  in  burning,  and  when  its  hydrogen  is  burned.  Therefore,  such  fuels  as 
sub-bituminous  coal  and  lignite,  which  are  high  in  moisture  content,  have  a  low  efficiency. 
However,  these  efficiencies  may  be  improved  if  the  stack  gases  are  cooled  to  room  tem- 
perature, by  heating  the  feed  water,  for  example. 

177 


HEATING  VENTILATING  AIR  CONDITIONING   GUIDE  1938 

6  •  What  are  the  advantages  of  a  sized  fuel  for  heating  furnaces? 

Because  a  sized  fuel  encourages  a  more  uniform  flow  of  air  through  the  bed,  the  burning 
will  be  more  uniform,  and  the  bed  will  be  less  liable  to  develop  holes  and  will  require  less 
attention.  Uniformity  of  fuel  size  is  more  desirable  as  the  area  of  the  bed  becomes 
smaller;  it  is  less  important  with  fuels  that  cake,  but  with  sized  fuels  the  caking  will  be 
more  uniform  and  the  air  flow  through  the  bed  will  be  steadier.  In  addition,  ash  and 
pieces  of  slate  are  less  likely  to  be  segregated  and  to  form  lumps  of  clinker. 

7  •  Does  the  size  of  a  fuel  affect  the  quantity  of  air  required  to  burn  it  at  a 
given  rate? 

The  total  air  required  to  give  the  same  gas  analysis  at  the  stack^is  independent  of  the 
size  of  the  fuel  burned,  but  for  non-caking  fuels  the  ratio  of  the  air  passing  through  the 
fuel  bed  to  the  total  air  entering  the  burner  base  decreases,  for  the  same^thickness  of  bed, 
as  the  size  of  the  fuel  becomes  smaller;  this  decrease  is  very  rapid  for  sizes  less  than  one 
inch.  For  coals  that  cake,  this  ratio  will  depend  on  the  way  the  caked  bed  is  broken  up 
and  on  the  size  of  the  resulting  pieces. 

8  •  Is  the  volatile  matter  which  is  given  off  when  coals  are  burned  of  the  same 
nature  in  all  coals? 

No.  The  products  given  off  by  coals  when  they  are  heated  differ  materially  in  the  ratios 
by  weight  of  the  gases  to  the  oils  and  tars.  No  heavy  oils  or  tars  are  given  off  by  anthra- 
cite, and  very  small  quantities  are  given  off  by  semi-anthracite.  As  the  volatile  matter 
in  the  coal  increases  to  as  much  as  40  per  cent  of  ash-free  and  moisture-free  coal,  in- 
creasing amounts  of  oils  and  tars  are  given  up.  For  coals  of  higher  volatile  content,  the 
relative  quantity  of  oils  and  tars  decreases,  so  it  is  low  in  the  sub-bituminous  coals  and 
in  lignite. 

9  •  Is  smoke  a  primary  product  hi  the  burning  of  fuels? 

Visible  smoke  may  include  very  small  particles  of  carbon,  oil,  tar,  water  (condensed 
steam),  and  ash.  Of  these,  the  oils,  tars,  and  ash  are  mainly  primary  products,  and  the 
water  is  partly  primary.  The  carbon,  which  usually  comprises  the  greater  part  of  the 
smoke,  results  from  the  breaking  up  by  heat  of  oils,  tars,  and  such  gases  as  methane,  so 
it  may  be  considered  a  secondary  product. 

10  •  Is  the  sulphur  in  coals  detrimental  to  combustion? 

Not  so  far  as  is  known,  but  its  complete  combustion  gives  only  25  per  cent  as  much  heat 
as  is  given  by  the  same  weight  of  carbon.  Sulphur  is  undesirable  because  it  causes  cor- 
rosion of  flues  and  stacks,  and  also  because  its  gases  pollute  the  atmosphere,  and  damage 
buildings  and  vegetation. 

11  •  How  do  deposits  of  soot  on  the  surfaces  of  a  boiler  or  heater  affect  the 
quantity  of  fuel  burned? 

There  are  two  effects.  The  scot  acts  as  an  insulating  layer  over  the  surface  and  reduces 
the  heat  transmission  to  the  water  or  air;  the  Bureau  of  Mines  Report  of  Investigations 
No.  3272  shows  that  the  loss  of  seasonal  efficiency  is  not  as  great  as  has  been  believed  and 
should  not  be  over  6  per  cent  because  the  greater  part  of  the  heat  is  transmitted  through 
the  firepot.  The  soot  clogs  the  passages  and  reduces  the  draft;  the  loss  of  efficiency 
from  this  action  may  be  much  more,  and  also  the  lack  of  draft  results  in  unsatisfactory 
heating. 


178 


Chapter  10 

CHIMNEYS  AND  DRAFT  CALCULATIONS 

Natural  Draft,  Mechanical  Draft,  Characteristics  of  Natural 
Draft  Chimneys,  Determining  Chimney  Sizes,  General  Equa- 
tion, Chimney  Construction,  Chimneys  for  Gas  Heating 

THE  design  and  construction  of  a  chimney  is  so  important  a  part 
of  the  heating  engineer's  work  that  a  general  knowledge  of  draft 
characterictics  and  calculations  is  essential. 

Draft,  in  general,  may  be  defined  as  the  pressure  difference  between  the 
atmospheric  pressure  and  that  at  any  part  of  an  installation  through 
which  the  gases  flow.  Since  a  pressure  difference  implies  a  head,  draft 
is  a  static  force.  While  no  element  of  motion  is  inferred,  yet  motion 
in  the  form  of  circulation  of  gases  throughout  an  entire  boiler  plant 
installation  is  the  direct  result  of  draft.  This  motion  is  due  to  the  pressure 
difference,  or  unbalanced  pressure,  which  compels  the  gases  to  flow.  Draft 
is  often  classified  into  two  kinds  according  to  whether  it  is  created 
thermally  or  artificially,  viz,  (1)  natural  or  thermal  draft,  and  (2)  arti- 
ficial or  mechanical  draft. 

Natural  Draft 

Natural  draft  is  the  difference  in  pressure  produced  by  the  difference  in 
weight  between  the  relatively  hot  gases  inside  a  natural  draft  chimney  and 
an  equivalent  column  of  the  cooler  outside  air,  or  atmosphere.  Natural 
draft,  in  other  words,  is  an  unbalanced  pressure  produced  thermally  by  a 
natural  draft  chimney  as  the  pressure  transformer  and  a  temperature 
difference.  The  intensity  of  natural  draft  depends,  for  the  most  part, 
upon  the  height  of  the  chimney  above  the  grate  bar  level  and  also  the 
temperature  difference  between  the  chimney  gases  and  the  atmosphere. 

A  typical  natural  draft  system  consists  essentially  of  a  relatively  tall 
chimney  built  of  steel,  brick,  or  reinforced  concrete,  operating  with  the 
relatively  hot  gases  which  have  passed  through  the  boilers  and  accessories 
and  from  which  all  the  heat  has  not  been  extracted.  Hot  gases  are  an 
essential  element  in  the  operation  of  a  natural  draft  system,  although 
inherently  a  heat  balance  loss. 

A  natural  draft  chimney  performs  the  two-fold  service  of  assisting  in 
the  creation  of  draft  by  aspiration  and  also  of  discharging  the  gases  at  an 
elevation  sufficient  to  prevent  them  from  becoming  a  nuisance. 

Natural  draft  is  quite  advantageous  in  installations  where  the  total  loss 
of  draft  due  to  resistances  is  relatively  low  and  also  in  plants  which  have 
practically  a  constant  load  and  whose  boilers  are  seldom  operated  above 

179 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


their  normal  rating.  Natural  draft  systems  have  been,  and  are  still  being, 
employed  in  the  operation  of  large  plants  during  the  periods  when  the 
boilers  are  operated  only  up  to  their  normal  rating.  When  the  rate  of 
operation  is  increased  above  the  normal  rating,  some  form  of  mechanical 
draft  is  employed  as  an  auxiliary  to  overcome  the  increased  resistances  or 
draft  losses.  Natural  draft  systems  are  used  almost  exclusively  in  the 
smaller  size  plants  where  the  amount  of  gases  generated  is  relatively  small 
and  it  would  be  expensive  to  install  and  operate  a  mechanical  draft 
system. 

The  principal  advantages  of  natural  draft  systems  may  be  summarized 
as  follows:    (1)  simplicity,  (2)  reliability,  (3)  freedom  from  mechanical 


FIG.  1.    GENERAL  OPERATING  CHARACTERISTICS  OF  TYPICAL  INDUCED  DRAFT  FAN 

parts,  (4)  low  cost  of  maintenance,  (5)  relatively  long  life,  (6)  relatively 
low  depreciation,  and  (7)  no  power  required  to  operate.  The  principal 
disadvantages  are:  (1)  lack  of  flexibility,  (2)  irregularity,  (3)  affected 
by  surroundings,  and  (4)  affected  by  temperature  changes. 

Mechanical  Draft 

^Artificial  draft,  or  mechanical  draft,  as  it  is  more  commonly  called,  is  a 
difference  in  pressure  produced  either  directly  or  indirectly  by  a  forced 
draft  fan,  an  induced  draft  fan,  or  a  Venturi  chimney  as  the  pressure 
transformer.  The  intensity  of  mechanical  draft  is  dependent  for  the  most 
part  upon  the  size  of  the  fan  and  the  speed  at  which  it  is  operated.  The 
element  of  temperature  does  not  enter  into  the  creation  of  mechanical 
draft  and  therefore  its  intensity,  unlike  natural  draft,  is  independent  of  the 
temperature  of  the  gases  and  the  atmosphere.  Mechanical  draft  includes 
the  induced  and  Venturi  types  of  draft  systems  in  which  the  pressure 
difference  is  the  result  of  a  suction,  and  also  the  forced  draft  system  in 
which  the  pressure  difference  is  the  result  of  a  blowing.  Mechanical  draft 
systems^tend  to  produce  a  vacuum  or  a  plenum,  as  the  system  used  in  its 
production  creates  a  pressure  difference  below,  or  above,  atmospheric 

1RO 


CHAPTER  10.   CHIMNEYS  AND  DRAFT  CALCULATIONS 


1 

, 

410 

X1 

"^ 

»ij 

5jn 

\ 

^ 

*S' 

A 

K 

4OO 

/ 

^ 

(i?> 

^ 

w 

fl. 

380 

ff1 

& 

^ 

•"* 

^ 

aeo 

^ 

»-, 

S 

s 

s 

.-.  u 

§ 

/ 

^ 

w 

V 

^ 

•34O 

z 

^ 

*s 

^ 

** 

V 

w 

it. 

£ 

s 

60  ? 

2320 

j. 

n* 

S  i 

o 

oe 

x 

•\r 

30O 

m 

^ 

\ 

> 

0. 

/ 

\ 

J0« 

290 

/ 

X 

-BO- 

260 

/ 

% 

j 

C 

K> 

4C 

0 

45 

O 

50 

0 

V* 

0 

•C 

0      «j 

to 

FIG.  2.  OPERATING  CHARACTERISTICS  OF  TYPICAL  CENTRIFUGAL  PUMP 

pressure,  respectively.    A  mechanical  draft  system  may  be  used  either  in 
conjunction  with,  or  as  an  adjunct  to,  a  natural  draft  system. 

Draft  Control 

To  obtain  the  maximum  efficiency  of  combustion,  a  definite  minimum 
supply  of  air  to  the  combustion  chamber  must  be  maintained.  To  pro- 
vide this  condition,  it  is  necessary  to  have  some  mechanical  means  of 
draft  control  or  adjustment,  because  of  variable  wind  velocities,  fluctua- 
tions in  atmospheric  temperatures  and  barometric  pressures,  and  their 
effect  upon  draft. 

For  this  purpose  there  are  various  mechanical  devices  which  auto- 
matically control  the  volume  of  air  admitted  to  the  combustion  chamber. 
Mechanical  draft  regulators  designed  to  control  or  adjust  draft,  should 


1.4 
1.2 
1.1 

S 

|0.8 

307 

*±0.6 

005 
.£ 
§0.4 
03 
0.2 
0.1 

°c 

—  —  ^ 

***•*, 

\ 

4*, 

i 

fe 

%; 

^ 

V 

ps 

*** 

.—  —  ' 

=x 

*-  -N 

"•x^ 

ff>c 

^ 

s^ 

\ 

\ 

¥ 

\ 

s. 

\j 

/ 

\ 

V 

\ 

/ 

\ 

\ 

\ 

/ 

\ 

^ 

\ 

/ 

\ 

,\ 

/ 

\ 

\ 

^ 

A 

)          30         60         90         120        150        180        210        240        270       30( 
Amount  of  Gases  Flowing  and  Discharged,  H>.  per  sea,  W 

FIG.  3.   TYPICAL  SET  OF  OPERATING  CHARACTERISTICS  OF  A  NATURAL  DRAFT  CHIMNEY 

181 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 

not  be  confused  with  mechanical  draft  systems  that  create  draft  mechani- 
cally, but  which  must  also  be  automatically  controlled. 

The  use  of  such  a  device  to  provide  a  more  uniform  and  dependable 
control  of  draft  than  could  be  maintained  by  manually  operated  dampers, 
will  produce  better  combustion  of  fuel.  This  higher  efficiency  of  combus- 
tion together  with  the  reduced  heat  losses  up  the  chimney  by  reason  of 
decreased  gas  velocity,  results  in  fuel  economy,  with  consequent  lower 
costs  of  plant  operation. 

CHARACTERISTICS  OF  CHIMNEYS 

In  order  to  analyze  the  performance  of  a  natural  draft  chimney,  it  may 
be  advantageous  to  compare  its  general  operating  characteristics  with 
those  of  a  centrifugal  pump  and  also  of  a  centrifugally-induced  draft  fan, 
there  being  a  similarity  among  the  three.  Figs.  1,  2  and  3  show  the 
general  operating  characteristics  of  a  typical  centrifugally-induced  draft 
fan,  a  typical  centrifugal  pump,  and  a  typical  natural  draft  chimney, 
respectively.  The  draft-capacity  curve  of  the  chimney  corresponds  to 
the  head-capacity  curve  of  the  pump  and  also  to  the  dynamic-head 
capacity  curve  of  the  fan. 

When  the  gases  in  the  chimney  are  stationary,  the  draft  created  is 
termed  the  theoretical  draft.  When  the  gases  are  flowing,  the  theoretical 
intensity  is  diminished  by  the  draft  loss  due  to  friction,  the  difference 
between  the  two  being  termed  the  total  available  draft.  The  general 
equation  for  this  net  total  available  draft  intensity  of  a  natural  draft 
chimney  with  a  circular  section  is  as  follows: 

D     -2Qfim?    (W*        W*\        0-00126  W»7V/£  m 

Pa  -  2.9ftOT0  (jr-jr) ^^ (D 

where 

D&  =  available  draft,  inches  of  water. 
H  —  height  of  chimney  above  grate  bars,  feet. 

BQ  ~  barometric  pressure  corresponding  to  altitude,  inches  of  mercury. 
W0  =  unit  weight  of  a  cubic  foot  of  air  at  0  F  and  sea  level  atmospheric  pressure, 

pounds  per  cubic  foot. 
Wc  —  unit  weight  of  a  cubic  foot  of  chimney  gases  at  0  F  and  sea  level  atmospheric 

pressure,  pounds  per  cubic  foot. 

To  «  absolute  temperature  of  atmosphere,  degrees  Fahrenheit. 
TC  =»  absolute  temperature  of  chimney  gases,  degrees  Fahrenheit. 
W  —  amount  of  gases  generated  in  the  combustion  chamber  of  the  boiler  and  passing 

through  the  chimney,  pounds  per  second. 
/  ~  coefficient  of  friction. 

L  =  length  of  friction  duct  of  the  chimney,  feet. 
D  =  minimum  diameter  of  chimney,  feet. 

The  first  term  of  the  right  hand  expression  of  Equation  1  represents 
the  theoretical  draft  intensity,  and  the  second  term,  the  loss  due  to  friction. 

Example  1.  _  Determine  the  available  draft  of  a  natural  draft  chimney  200  ft  in  height 
and  10  ft  in  diameter  operating  under  the  following  conditions:  atmospheric  tempera- 
ture, 62  F;  chimney  gas  temperature,  500  F;  sea  level  "atmospheric  pressure,  B0  =  29.92 
in.  of  mercury;  atmospheric  and  chimney  gas  density,  0.0863  and  0.09,  respectively; 
coefficient  of  friction,  0.016;  length  of  friction  duct,  200  ft.  The  chimney  discharges 
100  Ib  of  gases  per  second. 

182 


CHAPTER  10.   CHIMNEYS  AND  DRAFT  CALCUUITIONS 


Substituting  these  values  in  Equation  1  and  reducing: 


2.96  X  200  X  29.92  X 


0863      Q.09\       0.00126  X  100*  X  960  X  0.016  X  200 


/0.086S 
\   522 


960  / 


10*  X  29.92  X  0.09 


1.27  -  0.14  ~  1.13  in. 


Fig.  3  shows  the  variation  in  the  available  draft  of  a  typical  200  ft  by 
10  ft  chimney  operating  under  the  general  conditions  noted  in  Example  1. 
When  the  chimney  is  under  static  conditions  and  no  gases  are  flowing,  the 
available  draft  is  equal  to  1.27  in.  of  water,  the  theoretical  intensity.  As 
the  amount  of  gases  flowing  increases,  the  available  intensity  decreases 
until  it  becomes  zero  at  a  gas  flow  of  297  Ib  per  second,  at  which  point  the 
draft  loss  due  to  friction  is  equal  to  the  theoretical  intensity.  The  draft- 
capacity  curve  corresponds  to  the  head-capacity  curve  of  centrifugal 


ou 
29 

£28 
•5 
.£27 

§26 

£  25 
£24 
|  23 
m  22 

21 
20 

X 

'V,. 

\ 

\ 

s 

\ 

,. 

X 

^ 

^ 

s^ 

s>v 

*-x 

)         1000      2000      3000      4000      5000      6000     70C 
Corresponding  Altitude  above  Sea  Level,  ft 

FIG.  4.    RELATION  BETWEEN  BAROMETRIC  PRESSURE  AND  ALTITUDE 

pump  characteristics  and  the  dynamic-head-capacity  curve  of  a  fan.  The 
point  of  maximum  draft  and  zero  capacity  is  called  shut-off  draft,  or  point 
of  impending  delivery,  and  corresponds  to  the  point  of  shut-off  head  of  a 
centrifugal  pump.  The  point  of  zero  draft  and  maximum  capacity  is 
called  the  wide  open  point  and  corresponds  to  the  wide  open  point  of  a 
centrifugal  pump.  A  set  of  operating  characteristics  may  be  developed 
for  any  size  chimney  operating  under  any  set  of  conditions  by  substituting 
the  proper  values  in  Equation  1  and  then  plotting  the  results  in  the 
manner  shown  in  Fig.  3. 

In  substituting  the  values  for  the  various  factors  in  Equation  1,  care 
should  be  exercised  that  the  selections  be  as  near  the  actual  conditions  as 
is  practically  possible.  The  following  notes  will  serve  as  a  guide  for  these 
selections: 

1.  The  barometric  pressure  varies  inversely  as  the  altitude  of  the  plant  above  sea  level 
Fig.  4  gives  the  barometric  pressure  corresponding  to  various  elevations  as  computec 
from  the  equation  : 


where 


En  -  62,737  logi 

=  altitude  of  plant  above  sea  level,  feet. 

183 


(2 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 

In  general,  the  barometric  pressure  decreases  approximately  0.1  in.  of  mercury  per  100 
ft  increase  in  elevation. 

2.  The  unit  weight  of  a  cubic  foot  of  chimney  gases  at  0  F  and  sea  level  barometric 
pressure  is  given  by  the  equation: 

Wc  «  0.131  CO,  -f  0.095  02  -f  0.083  Nt  (3) 

In  this  equation  CO^  O*  and  Nt  represent  the  percentages  of  the  parts  by  volume  of  the 
carbon  dioxide,  oxygen  and  nitrogen  content,  respectively,  of  the  gas  analysis.  For 
ordinary  operating  conditions,  the  value  of  Wc  may  be  assumed  at  0.09. 

The  density  effect  on  the  chimney  gases  due  to  superheated  water  vapor  resulting 
from  moisture  and  hydrogen  in  the  fuel,  or  due  to  any  air  infiltrations  in  the  chimney 
proper  are  here  disregarded.  Though  water  vapor  content  is  not  disclosed  by  Orsat 
analysis,  its  presence  tends  to  reduce  the  actual  weight  per  cubic  foot  of  chimney  gases. 

3.  The  atmospheric  temperature  is  the  actual  observed  temperature  of  the  outside  air 
at  the  time  the  analysis  of  the  operating  chimney  is  made.    The  mean  atmospheric 
temperature  in  the  temperate  zone  is  approximately  62  F. 

4.  The  chimney  gas^  temperature  does  not  vary  appreciably  from  the  gas  temperature 
as  it  leaves  the  breeching  and  enters  the  chimney.    For  average  operating  conditions,  the 
chimney  gas  temperature  will  vary  between  500  F  and  650  F  except  in  the  case  when 
economizers  and  recuperators  are  used,  when  the  temperature  will  vary  between  300  F 
and  450  F.    If  a  chimney  has  been  properly  constructed,  properly  lined  and  has  no  air 
infiltration  due  to  open  joints,  the  temperature  of  the  gases  throughout  the  chimney  will 
not  differ  appreciably  from  the  foregoing  figures.    In  most  up-to-date  heating  plants,  the 
temperature  may  be  read  from  instruments  or  ascertained  from  a  pyrometer.     The 
analysis  of  this  section  is  predicated  on  the  assumption  of  constant  gas  temperature  and 
no  air  infiltration  throughout  the  height  of  the  chimney. 

5.  The  coefficient  of  friction  between  the  chimney  gases  and  a  sooted  surface  has  been 
taken  by  many  workers  in  this  field  as  a  constant  value  of  0.016  for  the  conditions  in- 
volved.   This  value,  of  course,  would  be  less  for  a  new  unlined  steel  stack  than  for  a 
brick  or  brick-lined  chimney,  but  in  time  the  inside  surface  of  all  chimneys  regardless  of 
the  materials  of  construction  becomes  covered  with  a  layer  of  soot,  and  thus  the  coef- 
ficient of  friction  has  been  taken  the  same  for  all  types  of  chimneys  and  in  general 
constant  for  all  conditions  of  operation.    For  reasons  of  simplicity  and  convenience  to 
the^reader,  this  constant  value  of  0.016  has  been  employed  in  the  development  of  the 
various  special  equations  and  charts  shown  in  this  chapter. 

However,  much  to  be  recommended  as  an  alternate  method  is  the  practise  of  separ- 
ately determining  duct  friction  factors  as  a  function  of  the  flow  conditions,  specifically 
as  a  function  of  the  Reynolds  number  and  the  relative  duct  roughness.  The  Reynolds 
criterion  is  based  on  the  physical  properties  of  the  gas,  the  duct  dimensions,  and  the  gas 
velocity.  The  gas  velocity  for  a  chimney  is  usually  well  above  the  critical  velocity. 
It  is  likely  that  this  procedure  of  using  a  separately  determined  variable  friction  factor 
for  chimney  flow  will  give  results  that  are  to  be  preferred  over  those  based  on  a  set 
constant. 

The  Reynolds  number,  a  dimensionless  ratio,  may  be  stated  as  follows: 

.    Cr=^  (4) 

where 

D  =  chimney  diameter,  feet. 
V  -  velocity  of  hot  gas,  feet  per  second, 
p  =  mass  density  of  the  chimney  gas  per  cubic  foot. 

(i  =  viscosity  of  the  gas  in  pounds-second  per  square  foot  taken  at  the  gas  tem- 
perature. 

In  another  form: 

1.27  W       0.039617 


184 


CHAPTER  10.   CHIMNEYS  AND  DRAFT  CALCUIATIONS 


where 


weight  of  gas  passed  per  second. 
acceleration  of  gravity. 


The  value  of  jj,  for  chimney  gases  is  usually  taken  as  that  of  air  or  nitrogen,  and  for  the 
variation  of  p,  with  temperature,  the  Sutherland  equation  may  be  employed  as  follows, 
giving  n  in  pounds-second  per  square  foot: 

f273  +  C\    f  Tc 

^  "  ^  Lrc  +  cj  L273 
where 

Tc  —  chimney  gas  temperature,  degrees  Centigrade. 
pLo  =  gas  viscosity  at  0  C. 
C  —  constant  for  specific  gas. 


Using  International  Critical  Table  values,  for  air 
nitrogen  IK>  =  34.5  X  10-8;  and  C  =  110. 


35.6  X  10-8;  C  =  12-4;  for 


0.010 


0.001 


40  60       80    100  200 

REYNOLDS  NUMBER,  IN  THOUSANDS 


FIG.  5.    VARIATION  OF  FRICTION  FACTOR  /  WITH  REYNOLDS  NUMBER 

Values  for  the  viscosity  of  air  and  of  nitrogen  (the  principal  component  of  chimney 
gases)  for  the  different  temperatures  follow,  in  which  the  values  given  in  pounds-second 
per  square  foot  are  to  be  multiplied  by  10-8: 


Temp.  F 

Air 

Nitrogen 


300 

49.7 

47.7 


400 

54.5 

52.2 


500 

58.5 

56.0 


600 

62.5 

59.8 


700 

66.7 

63.5 


800 

70.5 

67.0 


Example  2.  To  determine  the  Reynolds  number  Cr  for  a  flow  of  118  Ib  gas  per  second 
up  a  12  ft  diameter  chimney  at  a  temperature  of  500  F.  The  gas  may  be  assumed  to 
have  the  same  viscosity  as  nitrogen  at  500  F.  Using  Equation  5  : 


n  AO™ 
=  0.0396         = 


°-0396  X  118 


12 


x 


The  variation  of  the  friction  factor/  with  the  Reynolds  number  is  shown  in  Fig.  51. 
Three  curves  are  shown:  A,  B,  and  C,  where  the  choice  of  the  friction  factor  curve 
depends  on  the  relative  surface  roughness,  and  this  for  usual  chimney  construction  may 


iSee  also  Flow  of  Fluids  in  Closed  Circuits,  by  R.  J.  S.  Pigott  (Mechanical  Engineering,  August,  1933). 

185 


HEATING  VENTIIATINO  AIR  CONDITIONING  GUIDE  1938 


be  selected  by  size  since  surface  conditions  in  service  are  always  undetermmant.  For 
sizes  up  to  3  ft  in  diameter,  Curve  C  may  be  used;  from  3  to  6  ft,  Curve  B ;  and  from  6  ft 
upwards,  Curve  A.  Thus  for  the  previous  example  with  CT  =  698,000  and  12  ft  diameter, 
/  would  be  taken  from  Curve  A  as  0.0039. 

6.  The  length  of  the  friction  duct  is  the  vertical  distance  between  the  bottom  of  the 
breeching  opening  and  the  top  of  the  chimney.  Ordinarily  this  distance  is  approximately 
equal  to  the  height  of  the  chimney  above  the  grate  level. 


.001       .002       .003       .004       .005       .006 
Available  Draft  per  Ft  of  Height,  in.  of  Water 


.007 


FIG.  6.    CHIMNEY  PERFORMANCE  CHART* 

*ro  scive  a  typical  example:  Proceed  horizontally  from  a  Weight  Flow  Rate  point  to  intersection  with 
diameter  line;  from  this  intersection  follow  vertically  to  chimney  height  line;  from  this  intersection  follow 
horizontally  to  the  right  to  Available  Draft  scale.  Starting  from  a  point  of  Available  Draft,  take  steps  in 
reverse  order. 


7.  Assuming  no  air  infiltration  the  amount  of  gases  flowing  and  being  discharged  is, 
of  course,  equal  to  the  amount  of  gases  generated  in  the  combustion  chamber  of  the 
boiler.  The  total  products  of  combustion  in  pounds  per  second  for  a  grate-fired  boiler 
may  be  computed  from  the  equation: 


W  - 


where 


3600 


(6) 


C&  =  pounds  of  fuel  burned  per  square  foot  of  grate  surface  per  hour. 
G  ~  total  grate  surface  of  boilers,  square  feet. 
Cg  X  G  =  total  weight  of  fuel  burned  per  hour. 

Wtp  =  total  weight  of  products  of  combustion  per  pound  of  fuel. 

A  similar  computation  may  be  made  in  the  case  of  gas,  oil,  or  stoker-fired  fuel. 

186 


CHAPTER  10.   CHIMNEYS  AND  DRAFT  CALCUI»ATIONS 

Fig;  6  Is  a  typical  chimney  performance  chart  giving  the  available  draft 
intensities  for  various  amounts  of  gases  flowing  and  sizes  of  chimney. 
This  chart  is  based  on  an  atmospheric  temperature  of  62  F,  a  chimney  gas 
temperature  of  500  F,  a  unit  chimney  gas  weight  of  0.09  Ib  per  cubic  foot, 
sea  level  atmospheric  pressure,  a  coefficient  of  friction  of  0.016,  and  a 
friction  duct  length  equal  to  the  height  of  the  chimney  above  the  grate 
level.  These  curves  may  be  used  for  general  operating  conditions.  For 
specific  operating  conditions,  a  new  chart  should  be  constructed  from 
Equation  1. 

It  has  been  the  usual  custom,  and  still  is  to  a  lamentably  great  extent, 
to  select  the  required  size  of  a  natural  draft  chimney  from  a  table  of 
chimney  sizes  based  only  on  boiler  horsepowers.  After  the  ultimate 
horsepower  of  the  projected  plant  had  been  determined,  the  chimney  size 
in  the  table  corresponding  to  this  figure  was  then  selected  as  the  proper 
size  required.  Generally,  no  further  attempt  was  made  to  determine  if 
the  height  thus  selected  was  sufficient  to  help  create  the  required  draft 
demanded  by  the  entire  installation,  or  the  diameter  sufficiently  large  to 
enable  the  chimney  quickly,  efficiently,  and  economically  to  dispose  of  the 
gases.  Since  the  operating  characteristics  of  a  natural  draft  chimney  are 
similar  in  all  respects  to  those  of  a  centrifugal  pump,  or  a  centrifugal  fan, 
it  is  no  more  possible  to  select  a  proper  size  chimney  from  such  a  table, 
even  with  correction  factors  appended,  than  it  is  to  select  the  proper  size 
pump  from  tables  based  only  on  the  amount  of  water  to  be  delivered. 

DETERMINING  CHIMNEY  SIZES 

The  required  diameter  and  height  of  a  natural  draft  chimney  are  given 
by  the  following  equations: 


V*  (7) 

D  -  0.288  J    WTc  (8) 

*  B0WCV 

where 

H  =  required  height  of  chimney  above  grate  bar  level,  feet. 
D  =  required  minimum  diameter  of  chimney,  feet  (constant  for  entire  height), 
V  =  chimney  gas  velocity,  feet  per  second. 

pr  =  total  required  draft  demanded  by  the  entire  installation  outside  of  the  chimney, 
inches  of  water. 

Equations  7  and  8  give  the  required  size  of  a  natural  draft  chimney  with 
all  of  the  operating  factors  taken  into  consideration.  Values  for  all  of  the 
factors  with  the  exception  of  the  chimney  gas  velocity  may  be  either 
observed  or  computed.  It  is,  of  course,  necessary  to  assume  an  arbitrary 
value  for  the  velocity  in  order  to  arrive  at  some  definite  size.  For  any  one 
set  of  operating  conditions  tjiere  will  be  as  many  sizes  of  chimneys  as  there 
are  values  of  reasonable  velocities  to  assume.  Of  the  number  of  sizes 
corresponding  to  the  various  assumed  velocities,  there  is  one  size  which 
will  be  least  expensive.  Since  the  cost  of  a  chimney  structure,  regardless 

187 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

of  the  kind  of  material  used  in  the  construction,  varies  as  the  volume  of 
material  in  the  structure,  the  cost  criterion  then  may  be  represented  by 
the  approximate  equation  : 

Q  =  ttHD  (9) 

where 

Q  -  volume  of  material,  cubic  feet. 
t  —  average  wall  thickness,  feet. 

For  all  practical  purposes,  the  value  of  xt  may  be  taken  as  a  constant 
regardless  of  the  size  of  the  structure.  Hence,  in  general,  the  volume,  and 
consequently  the  cost,  of  a  chimney  structure  may  be  based  on  the  factor 
HD  as  a  criterion.  Therefore,  the  value  of  the  chimney  gas  velocity  which 
will  result  in  the  least  value  of  HD  for  any  one  set  of  operating  con- 
ditions will  produce  a  structure  which  will  be  the  most  economical  to  use, 
because  its  cost  will  be  least. 

The  problem  at  hand  is  to  deduce  an  equation  for  the  chimney  gas 
velocity  which  will  result  in  a  combination  of  a  height  and  a  diameter 
whose  product  HD  will  be  least.  The  solution  is  obtained  by  equating  the 
product  of  Equations  7  and  8  to  HD,  differentiating  this  product  with 
respect  to  V  and  equating  the  resulting  expression  to  zero.  This  pro- 
cedure results  in  the  following  expression  : 


772r      Q       c  2/5 

_TO" 

"  \ 
where  Fc  —  economical  chimney  gas  velocity,  feet  per  second. 

Equation  10  gives  the  economical  velocity  of  the  chimney  gases  for 
any  set  of  operating  conditions,  and  represents  the  velocity  which  will 
result  in  a  chimney  the  size  of  which  will  cost  less  than  that  of  any  other 
size  as  determined  by  any  other  velocity  for  the  same  operating  con- 
ditions. After  the  value  of  the  economical  velocity  has  been  determined, 
the  corresponding  height  and  diameter  can  then  be  determined  from 
Equations  7  and  8,  respectively,  and  the  economical  size  will  then  be 
attained.  Equations  7,  8  and  10  may  be  simplified  considerably  for 
average  operating  conditions  in  an  average  size  steam  plant  by  assuming 
typical  conditions. 

Average  chimney  gas  temperature,  500  F  .......  __________________  Tc  =  960 

Mean  atmospheric  temperature,  62  F  _____  .........................  TQ  =  522 

Average  coefficient  of  friction,  0.016  ____________________________________  ./  —  0.016 

Average  chimney  gas  density,  0.09.  ________________________________  Wc  =  0.09 

Sea  level  elevation,  with  barometer  of  29.92  _____  ...............  B0  -  29.92 

Substituting  these  values  in  Equations  10,  8  and  7,  respectively,  and 
reducing,  the  results  are  substantially: 


-  (11) 

D  -  1.5T72/5  (12) 

H  =  1901>r  (13) 
188 


CHAPTER  10.   CHIMNEYS  AND  DRAFT  CALCULATIONS 


Fig.  7  gives  the  economical  chimney  sizes  for  various  amounts  of  gases 
flowing  and  for  required  draft  intensities  as  computed  from  Equations  11, 
12  and  13.  They  are  based  on  the  operating  factors  used  in  reducing 
Equations  7,  8  and  10  to  their  simpler  form.  The  sizes  shown  by  the 
curves  in  the  chart  should  be  used  for  general  operating  conditions  only, 
or  for  installations  where  the  required  data  necessary  for  an  exact  deter- 


Height  of  Chimney,  ft. 
^0    25   50    75  100  125 150  1 75  200  225  250  275  300  325  350  371 


01234 


5     6     7     8     9    10    11   12 
Diameter  of  Chimney,  ft 


13    14  15° 


FIG.  7.    ECONOMICAL  CHIMNEY  SizEsa 

aDiameter  values  also  for  gas  temperatures  of  400,  500  and  600  F 


mination  are  difficult  or  impossible  to  secure.  Whenever  it  is  possible  to 
secure  accurate  data,  or  the  anticipated  operating  conditions  are  fairly 
well  known,  the  required  size  should  be  determined  from  Equations  7, 
8  and  10.  The  recommended  minimum  inside  dimensions  and  heights  of 
chimneys  for  small  and  medium  size  installations  are  given  in  Table  1. 


GENERAL  EQUATION 

The  general  draft  equation  for  a  steam  producing  plant  may  be  stated 
as  follows: 

0t  -  Af  -  *F  +  AB  -h  ted  +  feC  +  feBr  +  &V  +  ho  +  &B  +  &R  (14) 

189 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

where 

Dt  »  theoretical  draft  intensity  created  by  pressure  transformer,  inches  of  water. 
/?f  =  draft  loss  due  to  friction  in  pressure  transformer,  inches  of  water. 
feF  =  draft  loss  through  the  fuel  bed,  inches  of  water. 
&B  =  draft  loss  through  the  boiler  and  setting,  inches  of  water. 
JiEr  =  draft  loss  through  the  breeching,  inches  of  water. 
kv  —  draft  loss  due  to  velocity,  inches  of  water. 
&Bd  =  draft  loss  due  to  bends,  inches  of  water. 
he  =  draft  loss  due  to  contraction  of  opening,  inches  of  water. 
ho  =  draft  loss  due  to  enlargement  of  opening,  inches  of  water. 
&E  ==  draft  loss  through  the  economizer,  inches  of  water. 
&R  =  draft  loss  through  recuperators,  regenerators,  or  air  heaters,  inches  of  water. 

The  left  hand  member  of  Equation  14  represents  the  total  amount  of 
available  draft  created  by  the  pressure  transformer,  that  is,  the  natural 
draft  chimney,  Venturi  chimney,  or  fan,  and  is  equal  to  the  theoretical 
intensity  less  the  internal  losses  incidental  to  operation.  The  right  hand 
member  represents  the  sum  of  all  of  the  various  losses  of  draft  throughout 
the  entire  boiler  plant  installation  outside  of  the  pressure  transformer 
itself.  The  left  hand  member  expresses  the  available  intensity  and  is 
analogous  to  the  head  developed  by  a  centrifugal  pump  in  a  water  works 
system,  while  the  right  hand  member  expresses  the  required  draft  in- 
tensity and  is  analogous  to  the  total  dynamic  head  in  a  water  works 
system.  For  a  general  circulation  of  gases 

AL  -  Dr  (15) 

where 

.Da  —  available  draft  intensity,  inches  of  water. 
Pr  =  required  draft,  inches  of  water. 

The  draft  loss  through  the  fuel  bed  (ftp),  or  the  amount  of  draft  required  to 
effect  a  given  or  required  rate  of  combustion,  varies  between  wide  limits 
and  represents  the  greater  portion  of  the  required  draft.  In  coal-fired 
installations,  the  draft  loss  through  the  fuel  bed  is  dependent  upon  the 
following  factors:  (1)  character  and  condition  of  the  fuel,  clean  or  dirty; 
(2)  percentage  of  ash  in  the  fuel;  (3)  volume  of  interstices  in  the  fuel  bed, 
coarseness  of  fuel;  (4)  thickness  of  the  fuel  bed,  rate  of  combustion; 
(5)  type  of  grate  or  stoker  used;  (6)  efficiency  of  combustion. 

There  is  a  certain  intensity  of  draft  with  which  the  best  results  will  be 
obtained  for  every  kind  of  coal  and  rate  of  combustion.  Fig.  8  gives  the 
intensity  of  draft,  or  the  vacuum  in  the  combustion  chamber  required  to 
burn  various  kinds  of  coal  at  various  rates  of  combustion.  Expressed  in 
other  words,  these  curves  represent  the  amount  of  draft  required  to  force 
the  necessary  amount  of  air  through  the  fuel  bed  in  order  to  effect  various 
rates  of  combustion.  It  will  be  noted  that  the  amount  of  draft  increases 
as  the  percentage  of  volatile  matter  diminishes,  being  comparatively  low 
for  the  lower  grades  of  bituminous  coals  and  highest  for  the  high  grades 
and  small  sizes  of  anthracites.  Also,  when  the  interstices  of  the  coal  are 
large  and  the  particles  are  not  well  broken  up,  as  with  bituminous  coals, 
much  less  draft  is  required  than  when  the  particles  are  small  and  are  well 

190 


CHAPTER  10.   CHIMNEYS  AND  DRAFT  CALCULATIONS 


broken  up,  as  with  bituminous  slack  and  the  small  sizes  of  anthracites.  In 
general,  the  draft  loss  through  the  fuel  bed  increases  as:  (1)  the  per- 
centage of  volatile  matter  diminishes;  (2)  the  percentage  of  fixed  carbon 
increases;  (3)  the  thickness  of  the  bed  increases;  (4)  the  percentage  of  ash 
increases;  (5)  the  volume  of  the  interstices  diminishes. 

In  making  the  preliminary  assumptions  for  the  draft  loss  through  the 
fuel  bed,  due  allowances  should  be  made  for  a  possible  future  change  in 
the  grade  of  fuel  to  be  burned  and  also  in  the  rate  of  combustion.  A  value 


TABLE  1. 


RECOMMENDED  MINIMUM  CHIMNEY  SIZES  FOR 
HEATING  BOILERS  AND  FURNACES* 


RECTANGULAR  FLUB 

ROUND  FLTIK 

WARM  Am 

STEAM 

TTT    ^ 

NOMINAL 

FtJRNACl 

CAPACITY 

or  LEADER 
PTPB 

BOILER 
CAPACITY 
SQFr 
OF  RADI- 
ATION 

WATER 
HEATER 
CAPACITY 

or  RADI- 
ATION 

DIMEN- 
SIONS or 

FlRVCliAT 

LINING 
IN  INCHES 

Actual 
Inside 

of  Fire  Clay 

Actual 
Area 
Sq  In. 

Inside 
Diam- 
eter of 
Lining 
in 

Actual 
Area 
Sq  In. 

HEIGHT 
IN  FT 
ABOTV 
GRATJB 

in  Inches 

Inches 

790 

590 

973 

8^x13 

7     xllJi 

81 

35 

1000 

690 

1,140 

10 

79 

900 

1,490 

13x13 

HJixllJi 

127 

900 

1,490 

8^x18 

6?4  x  16j2 

110 

1,100 

1,820 

12 

113 

40 

1,700 

2,800 

13x18 

HJ^xl6J-i 

183 

1,940 

3,200 

15 

177 

2,130 

3,520 

18x18 

15Jixl5Ji 

248 

2,480 

4,090 

20x20 

17J^xl7}i 

298 

45 

3,150 

5,200 

18 

254 

50 

4,300 

7,100 

20 

314 

4,600 

7,590 

20x24 

17x21 

357 

5,000 

8,250 

24x24 

21x21 

441 

55 

5,570 

9,190 

24x24° 

576 

60 

5,580 

9,200 

22 

380 

6,980 

11,500 

24 

452 

65 

7,270 

12,000 

24x28b 

672 

8,700 

14,400 

28x28b 

784 

9,380 

15,500 

27 

573 

10,150 

16,750 

30x30b 

900 

10,470 

17,250 

28x32b 

896 

aTbis  table  is  taken  from  the  A.S.H.V.E.  Code  of  Minimum  Requirements  for  the  Heating  and  Venti- 
lation of  Buildings  (Edition  of  1929). 

bDimensions  are  for  unlined  rectangular  flues, 

should  be  selected  for  this  loss  which  will  represent  not  only  the  highest 
rate  of  combustion  which  will  be  encountered,  but  also  the  grade  of  coal 
which  has  the  greatest  resistance  through  the  fuel  bed  and  which  may  be 
burned  at  a  later  date. 

In  powdered-fuel  and  oil-fired  installations,  there  will  be  no  draft  loss 
through  the  fuel  bed  since  there  is  none  and,  consequently,  this  factor 
becomes  zero  in  the  general  draft  equation.  All  other  factors  being 
constant,  the  height  of  the  chimney  in  installations  of  this  character  will 
be  less  than  the  height  in  coal-fired  installations,  and  in  the  case  of  me- 
chanical draft  installations  the  driving  units  need  not  be  as  large  since  the 
head  against  which  the  fan  is  to  operate  is  not  as  great  in  the  former  as 
in  the  latter. 

191 


HEATING  VENTILATING   AIR  CONDITIONING   GUIDE  1938 


The  draft  loss  through  the  boiler  and  setting  (As)  also  varies  between  wide 
limits  and,  in  general,  depends  upon  the  following  factors: 

1.  Type  of  boiler.  5.  Arrangement  of  baffles. 

2.  Size  of  boiler.  6.  Type  of  grate. 

3.  Rate  of  operation.  7.  Design  of  brickwork  setting. 

4.  Arrangement  of  tubes.  8.  Excess  air  admitted. 

9.  Location  of  entrance  into  breeching. 

Curves  showing  the  draft  loss  through  the  boiler  are  usually  based  on 
the  load  or  quantity  of  gases  passing  through  the  boiler,  expressed  in 
terms  of  percentage  of  normal  rate  of  operation.  Owing  to  the  great 
variety  of  boilers  of  different  designs  and  the  various  schemes  of  baffling, 
it  is  impossible  to  group  together  a  set  of  curves  for  the  draft  loss  through 


0  5          10         15         20         25          30         35         40        45 

POUNDS  OF  COAL  BURNED  PER  SQ  FT  OF  GRATE  SURFACE  PER  HOUR 

FIG.  8.    DRAFT  REQUIRED  AT  DIFFERENT  RATES  OF  COMBUSTION 
FOR  VARIOUS  KINDS  OF  COAL 

the  boiler  which  may  even  be  used  generally.  It  is  therefore  necessary  to 
secure  this  information  from  the  manufacturer  of  the  particular  type  of 
boiler  and  baffle  arrangement  under  consideration. 

When  a  boiler  is  installed  and  in  operation,  the  draft  loss  depends  upon 
the  amount  of  gases  flowing  through  it.  This,  in  turn,  depends  upon  the 
proportion  of  excess  air  admitted  for  combustion.  Primarily,  the  amount 
of  excess  air  is  measured  by  the  COZ  content;  the  less  the  amount  of  C02, 
the  greater  the  amount  of  excess  air  and  hence  the  greater  the  draft  loss. 

The  loss  of  draft  through  the  boiler  will  vary  directly  as  the  size  of  the 
boiler  and  the  length  of  the  gas  passages  within.  The  loss  also  varies  as 
the  number  of  tubes  high,  but  not  in  a  direct  ratio  inasmuch  as  the  loss 
due  to  the  reversal  of  flow  at  the  ends  of  the  baffles  remains  constant 
regardless  of  the  height  of  the  boiler.  The  arrangement  of  the  tubes, 
whether  the  gases  flow  parallel  to  or  at  right  angles  to  the  tubes,  has  an 
appreciable  effect  on  the  loss.  The  arrangement  of  the  baffles  influences 
the  draft  loss  greatly,  the  loss  through  a  boiler  with  five  passes  being 

192 


CHAPTER  10.   CHIMNEYS  AND  DRAFT  CAIICULATIONS 

greater  than  the  loss  through  one  of  three  or  four  passes.  A  poor  design 
and  a  rough  condition  of  the  brickwork  will  increase  the  loss  greatly, 
whereas  a  proper  design  and  a  smooth  condition  will  keep  the  loss  at  a 
minimum.  The  loss  through  the  boiler  will  be  less  when  the  breeching 
entrance  is  located  at  or  near  the  top  of  the  boiler  than  when  it  is  located 
at  or  near  the  bottom  since  the  gases  have  a  shorter  distance  to  travel 
in  the  former  instance. 

The  draft  loss  through  the  breeching   (&Br)   is   given  by  the  general 
equation  : 


where 

W  =  the  amount  of  gases  flowing,  pounds  per  second. 

Tc  =  absolute  temperature  of  breeching  gases,  degrees  Fahrenheit. 

/  =  coefficient  of  friction. 

L  —  length  of  breeching,  feet. 

A  =  area  of  breeching,  square  feet. 

BQ  =  atmospheric  pressure  corresponding  to  altitude,  inches  of  mercury. 
Wc  =  weight  of  a  cubic  foot  of  breeching  gases  at  0  F  and  sea  level  atmospheric 

pressure;  pounds  per  cubic  foot. 
Cbr  =  hydraulic  radius  of  breeching  section. 

It  has  been  the  general  custom  to  lump  off  the  intensity  of  the  breeching 
loss  at  0.10  in.  of  water  per  100  ft  of  breeching  length  regardless  of  its  size 
or  shape  or  the  amount  and  temperature  of  the  gases  flowing  through  it. 
This  practice  is  hazardous  and  has  no  more  foundation  in  fact  than  that  of 
determining  the  friction  head  in  a  water  works  system  without  taking 
into  consideration  the  size  of  the  pipe  or  the  amount  of  water  flowing 
through  it.  When  the  length  of  the  breeching  is  relatively  short,  any 
variation  in  any  one  of  the  factors  in  the  equation  will  have  no  appreciable 
effect  on  the  draft  loss.  However,  when  the  breeching  is  relatively  long, 
the  draft  loss  is  affected  greatly  by  the  various  factors,  particularly  by  the 
size  and  shape  as  well  as  by  the  weight  of  gases  flowing. 

The  draft  loss  due  to  velocity  (hv)  is  given  by  the  equation 

0.000194W»rc 

hv  = 


and  represents  the  amount  of  draft  required  to  accelerate  the  gases  from 
zero  velocity  to  the  velocity  at  which  the  gases  are  flowing,  or  in  other 
words,  from  a  static  gas  condition  of  zero  flow  to  the  amount  of  gases 
flowing  throughout  the  installation.  This  loss  corresponds  to  the  velocity 
head  in  water  works  systems. 

The  draft  loss  due  to  bends  (&Bd)  is  equivalent  to  the  loss  due  to  the 
velocity  head  for  a  90-deg  bend.  In  changing  direction  of  flow,  the  gas 
velocity  decreases  to  zero  with  a  loss  of  velocity  head  and  then  increases 
to  its  proper  value  at  the  expense  of  a  loss  in  pressure  head,  the  net  result 
being  a  loss  in  pressure  head  equal  to  the  velocity  head  at  the  bend. 
This  loss  is  given  by  the  equation: 


193 


HEATING  VENTILATING  AIR  CONDITIONING   GUIDE  1938 

The  friction  at  a  right-angle  bend  is  sometimes  expressed  as  the 
equivalent  of  a  straight  length  of  flue  of  a  certain  length  for  a  certain 
diameter,  similar  to  the  procedure  used  in  estimating  the  loss  due  to 
bends  in  piping  systems  conducting  water.  Most  flues,  however,  par- 
ticularly breechings,  are  built  square  or  rectangular  in  section  and  no 
general  equation  based  on  the  shape  of  the  flue  can  be  conveniently 
expressed. 

The  draft  loss  due  to  sudden  contraction  of  an  area  (he)  is  given  by  the 
equation  : 


C=          A*9B0WC 
where 

JTC  —  coefficient  of  sudden  contraction  based  on  —-,  the  ratio  of  the  areas  of  the 


smaller  to  the  larger  section  =  0.5  {  1  —  —r-  j 


As  =  area  of  the  smaller  section. 

When  the  flue  or  passage  through  which  the  gases  flow  is  suddenly 
contracted,  a  considerable  portion  of  the  static  head  in  the  larger  section 
is  converted  into  velocity  head  and  a  draft  loss  of  some  consequence,  par- 
ticularly in  a  short  breeching,  takes  place.  A  sudden  contraction  should 
always  be  avoided  where  possible.  At  times,  however,  due  to  obstruc- 
tions or  limited  head-room,  it  is  necessary  to  alter  the  size  of  the  breeching, 
but  a  sudden  contraction  may  be  avoided  by  gradually  decreasing  the 
area  over  a  length  of  several  feet. 

The  draft  loss  due  to  a  sudden  enlargement  of  an  area  (ho)  is  given  by  the 
equation  : 


where 

K0  =  coefficient  of  sudden  enlargement  based  on  -^,  the  ratio  of  the  areas  of  the 


small 


ter  to  the  larger  section  =  f  1  -  -p  J 


When  the  flue  or  passage  through  which  the  gases  flow  is  suddenly 
enlarged,  a  portion  of  the  velocity  head  is  converted  into  static  head  in  the 
larger  section  and,  like  the  loss  due  to  sudden  contraction,  a  loss  of  some 
consequence,  particularly  in  short  breechings,  takes  place.  A  sudden 
enlargement  in  a  breeching  may  be  avoided  by  gradually  increasing  the 
area  over  a  length  of  several  feet.  In  large  masonry  chimneys,  the  area  of 
the  flue  at  the  region  of  the  breeching  entrance  is  considerably  larger 
than  the  area  of  the  breeching  at  the  chimney,  and  a  sudden  enlargement 
exists. 

The  draft  loss  through  the  economizer  (&E)  should  be  obtained  from  the 
manufacturer  but  for  general  purposes  it  may  be  computed  from  the 
following  general  equation  : 


ft.  =      'c  (31) 

10* 

194 


CHAPTER  10.   CHIMNEYS  AND  DRAFT  CALCULATIONS 

where 

Wn  =  pounds  of  gases  flowing  per  hour  per  linear  foot  of  pipe  in  each  economizer 

section. 
N  —  number  of  economizer  sections. 

An  economizer  in  a  steam  plant  affects  the  draft  in  two  ways,  (1)  it 
offers  a  resistance  to  the  flow  of  gases,  and  (2)  it  lowers  the  average 
chimney  gas  temperature,  thereby  decreasing  the  available  intensity.  In 
the  case  of  a  natural  draft  installation,  both  of  these  factors  result  in  a 
relative  increase  in  the  height  of  the  chimney  and,  in  the  case  of  a  large 
plant,  they  may  add  as  much  as  20  or  30  ft  to  the  height.  The  decrease 
in  the  temperature  of  the  gases  after  they  have  passed  through  the 
economizer  has  an  extremely  important  effect  on  the  performance  of  a 
natural  draft  chimney  and  also  upon  the  performance  of  a  fan. 

CpNSTHUCTION  DETAILS 

For  general  data  on  the  construction  of  chimneys  reference  should  be 
made  to  the  Standard  Ordinance  for  Chimney  Construction  of  the 
National  Board  of  Fire  Underwriters.  Briefly  summarized,  these  provisions 
are  as  follows  for  heating  boilers  and  furnaces: 

The  construction,  location,  height  and  area  of  the  chimney  to  which  a  heating  boiler 
or  warm-air  furnace  is  connected  affect  the  operation  of  the  entire  heating  system.  Most 
residence  chimneys  are  built  of  brick  and  may  be  either  lined  or  unlined,  but  in  either 
case  the  walls  must  be  air-tight  and  there  should  be  only  one  smoke  opening  into  the 
chimney.  Cleanout,  if  provided,  must  be  absolutely  air-tight  when  closed. 

The  walls  of  brick  chimneys  shall  be  not  less  than  3%  in.  thick  (width  of  a  standard 
size  brick)  and  shall  be  lined  with  fire-clay  flue  lining.  Fire-clay  flue  linings  shall  be 
manufactured  from  suitable  refractory  clay,  either  natural  or  compounded,  and  shall 
be  adapted  to  withstand  high  temperatures  and  the  action  of  flue  gases.  They  shall  be 
of  standard  commercial  thickness,  but  not  less  than  %  in.  All  fire-clay  flue  linings  shall 
meet  the  standard  specification  of  the  Eastern  Clay  Products  Association.  The  flue 
sections  shall  be  set  in  special  mortar,  and  shall  have  the  joints  struck  smooth  on  the 
inside.  The  masonry  shall  be  built  around  each  section  of  lining  as  it  is  placed,  and  all 
spaces  between  masonry  and  linings  shall  be  completely  filled  with  mortar.  No  broken 
flue  lining  shall  be  used.  Flue  lining  shall  start  at  least  4  in.  below  the  bottom  of  smoke- 
pipe  intakes  of  flues,  and  shall  be  continued  the  entire  heights  of  the^flues  and  project 
at  least  4  in.  above  the  chimney  top  to  allow  for  a  2  in.  projection  of  lining.  The  wash  or 
splay  shall  be  formed  of  a  rich  cement  mortar.  To  improve  the  draft  the  wash  surface 
should  be  concave  wherever  practical. 

Flue  lining  may  be  omitted  in  brick  chimneys,  provided  the  walls  of  the  chimneys 
are  not  less  than  8  in.  thick,  and  that  the  inner  course  shall  be  a  refractory  clay  brick. 
All  brickwork  shall  be  laid  in  spread  mortar,  with  all  joints  push-filled.  Exposed  joints 
both  inside  and  outside  shall  be  struck  smooth.  No  plaster  lining  shall  be  permitted. 

Chimneys  shall  extend  at  least  3  ft  above  flat  roofs  and  2  ft  above  the  ridges  of  peak 
roofs  when  such  flat  roofs  or  peaks  are  within  30  ft  of  the  chimney.  The  chimney 
shall  be  high  enough  so  that  the  wind  from  any  direction  shall  not  stnke  the  top  of  the 
chimney  from  an  angle  above  the  horizontal.  The  chimney  shall  be  properly  capped  with 
stone,  terra  cotta,  concrete,  cast-iron,  or  other  approved  material;  but  no  such  cap 
or  coping  shall  decrease  the  flue  area. 

There  shall  be  but  one  connection  to  the  flue  to  which  the  boiler  or  furnace  smoke- 
pipe  is  attached.  The  boiler  or  furnace  smoke-pipe  shall  be  thoroughly  grouted  into  the 
chimney  and  shall  not  project  beyond  the  inner  surface  of  the  flue  lining. 

The  size  or  area  of  flue  lining  or  of  brick  flue  for  warm-air  furnaces  depends  on  height 
of  chimney  and  capacity  of  heating  system.  For  chimneys  not  less  than  35  ft  in  height 
above  grate  line,  the  net  internal  dimensions  of  lining  should  be  at  least  7  x  11 H  in. 

195 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


for  a  total  leader  pipe  area  up  to  790  sq  in.  Above  790  and  up  to  1,000  sq  in.  of  leader 
pipe  area  the  lining  should  be  at  least  11^  x  11  %  in.  inside.  In  case  of  brick  flues  not 
less  than  35  ft  in  height  with  no  linings,  the  internal  dimensions  should  be  at  least 
8  x  12  in.  up  to  790  sq  in.  of  leader  area,  and  at  least  12  x  12  in.  for  leader  capacities  up  to 
1,000  sq  in.  Chimneys  under  35  ft  in  height  are  unsatisfactory  in  operation  and  hence 
should  be  avoided. 

CHIMNEYS  FOR  GAS  HEATING 

The  burning  of  gas  differs  from  the  burning  of  coal  in  that  the  force 
which  supplies  the  air  for  combustion  of  the  gas  comes  largely  from  the 
pressure  of  the  gas  in  the  supply  pipe,  whereas  air  is  supplied  to  a  bed  of 
burning  coal  by  the  force  of  the  chimney  draft.  If,  with  a  coal-burning 
boiler,  the  draft  is  poor,  or  if  the  chimney  is  stopped,  the  fire  is  smothered 
and  the  combustion  rate  reduced.  In  a  gas  boiler  or  furnace  such  a 
condition  would  interfere  with  the  combustion  of  the  gas,  but  the  gas 
would  continue  to  pass  to  the  burners  and  the  resulting  incomplete  com- 
bustion would  produce  a  dangerous  condition.  In  order  to  prevent  incom- 
plete combustion  from  insufficient  draft,  all  gas-fired  boilers  and  furnaces 
should  have  a  back-draft  diverter  in  the  flue  connection  to  the  chimney. 

TABLE  2.    SUGGESTED  GENERAL  DIMENSIONS  FOR  VERTICAL  BACK-DRAFT  DIVERTER 


Table  of  Dimensions  (In.) 


PIPE 
SIZE 

A 

B 

C 

D 

E 

P 

G 

H 

I 

J 

K 

L 

M 

3 

3 

3 

5.5 

7.0 

3.8 

0.7 

4.4 

3.0 

1.5 

2.5 

0.7 

1.5 

2.3 

4 

4 

4 

7.2 

9.5 

5.0 

1.0 

6.0 

4.0 

2.0 

3.5 

1.0 

2.0 

3.0 

5 

5 

5 

9.4 

10.8 

5.3 

1.5 

8.0 

5.0 

2.3 

4.0 

0.9 

2.4 

3.5 

6 

6 

6 

11.5 

12.0 

5.6 

1.9 

9.8 

6.0 

2.5 

4.5 

0.8 

2.7 

4.0 

7 

7 

7 

13.5 

13.9 

6.4 

2.3 

11.6 

7.0 

2.9 

5.3 

0.9 

3.1 

4.6 

8 

8 

8 

15.5 

15.8 

7.1 

2.7 

13.4 

8.0 

3.2 

6.0 

1.0 

3.5 

5.3 

9 

9 

9 

17.5 

17.5 

7.7 

3.1 

15.2 

9.0 

3.5 

6.7 

1.0 

4.0 

5.8 

10 

10 

10 

19.7 

18.8 

7.9 

3.6 

17.2 

10.0 

3.8 

7.3 

1.0 

4.3 

6.2 

11 

11 

11 

22.2 

20.7 

8.4 

4.3 

19.6 

11.0 

4.1 

8.0 

1.5 

4.6 

6.6 

12 

12 

12 

24.7 

22.2 

8.7 

5.0 

22.0 

12.0 

4.4 

8.5 

1.7 

5.0 

7,0 

196 


CHAPTER  10.   CHIMNEYS  AND  DRAFT  CALCUIATIONS 


A  study  of  a  typical  back-draft  diverter  shows  that  partial  or  complete 
chimney  stoppage^will  merely  cause  some  of  the  products  of  combustion 
to  be  vented  out  into  the  boiler  room,  but  will  not  interfere  with  com- 
bustion^ In  fact,  gas-designed  appliances  must  perform  safely  under  such 
a  condition  to  be  approved  by  the  American  Gas  Association  Laboratory. 
Other  functions  of  the  back-draft  diverter  are  to  protect  the  burner  and 
pilot  from  the  effects  of  down-drafts,  and  to  neutralize  the  effects  of 
variable  chimney  drafts,  thus  maintaining  the  appliance  efficiency  at  a 
substantially  constant  value.  Converted  boilers  or  furnaces,  as  well  as 
gas-designed  appliances,  should  be  provided  with  back-draft  diverters. 

Since  back-draft  diverters  have  a  special  function  to  perform  in  pro- 
tecting gas  burning  appliances,  it  is  necessary  that  they  should  be  built 
to  the  proper  size  as  shown  in  Table  2  for  a  vertical  type  and  in  Table  3 
for  a  horizontal  arrangement.  Equipment  of  this  kind  listed  by  the 
American  Gas  Association  Testing  Laboratory  must  bear  the  listing 
symbol  A.G.A. 


.     SUG 

GESTED  GENERAL  DIMENSIONS  FOR  HORIZONTAL  BACK-DRAFT  DIVERTER 

t 
,             r  ,._       tei   n 

1 
[ 

i 
) 

r" 

~i 

^  /-Baffle 
1       /  / 

r 

^ 

E 

E 

3 

( 

•  —  1-\-  —  1 

L 

Baffle 

^  \ 

Baffle 
strap 

nlet 

-Relief  opening  *^ 

Table  of  Dimensions  (In.) 


PIPE 

SIZE 

A 

B 

C 

D 

E 

F 

G 

H 

I 

J 

E 

L 

M 

3 

3 

3 

6 

1.5 

4.8 

3.8 

1.4 

2.5 

2,5 

2.5 

2.1 

0  6 

1.8 

4 

4 

4 

8 

2.0 

4.8 

5.0 

1.9 

3.4 

3.4 

3.4 

2.9 

0.8 

2.3 

5 

5 

5 

10 

2.5 

4.8 

6.3 

2.4 

4.2 

4.2 

4.2 

3.5 

0.9 

2.9 

6 

6 

6 

12 

3.0 

4.8 

7.5 

2.9 

5.0 

5.0 

5.0 

4.3 

1.1 

3.5 

7 

7 

7 

14 

3.5 

4.8 

8.8 

3.4 

5.9 

5.9 

5.9 

5.0 

1.3 

4.1 

8 

8 

8 

16 

4.0 

4.8 

10.0 

3.9 

6.7 

6.7 

6.7 

5.6 

1.5 

4.7 

9 

9 

9 

18 

4.5 

4.8 

11.3 

4.4 

7.5 

7.5 

7.5 

6.4 

1.7 

5.3 

10 

10 

10 

20 

5.0 

4.8 

12.5 

4.9 

8.4 

8.4 

8.4 

7.0 

1.9 

5.8 

11 

11 

11 

22 

5.5 

4.8 

13.8 

5.4 

9.2 

9.2 

9.2 

7.8 

2.1 

6.4 

12 

12 

12 

24 

6.0 

4.8 

15.0 

5.9 

10.0 

10.0 

10.0 

8.5 

2.3 

7.0 

197 


HEATING  VENTIUITING  AIR  CONDITIONING   GUIDE  1938 


As  is  the  case  with  the  complete  combustion  of  almost  all  fuels,  the 
products  of  combustion  for  gas  are  carbon  dioxide  (C09)  and  water  vapor 
with  just  a  trace  of  sulphur  tripxide  (503).  Sulphur  usually  burns  to  the 
trioxide  in  the  presence  of  an  iron  oxide  catalyst.  The  volume  of  water 
vapor  in  the  flue  products  is  about  twice  the  volume  of  the  carbon  dioxide 
when  coke  oven  or  natural  gas  is  burned.  Because  of  the  large  quantity 
of  water  vapor  which  is  formed  by  the  burning  of  gas,  it  is  quite  important 
that  all  gas-fired  central  heating  plants  be  connected  to  a  chimney  having 
a  good  draf t.^  Lack  of  chimney  draft  causes  stagnation  of  the  products  of 
combustion  in  the  chimney  and  results  in  the  condensation  of  a  large 
amount  of  the  water  vapor.  A  good  chimney  draft  draws  air  into  the 
chimney  through  the  openings  in  the  back-draft  diverter,  lowers  the  dew 
point  of  the  mixture,  and  reduces  the  tendency  of  the  water  vapor  to 
condense. 

The  flue  connections  from  a  gas-fired  boiler  or  furnace  to  the  chimney 
should  be  of  a  non-corrosive  material.  In  localities  where  the  price  of 

TABLE  4.    MINIMUM  ROUND  CHIMNEY  DIAMETERS  FOR  GAS  APPLIANCES  (INCHES) 


HJCIOHT  or 

GAS  CONSUMPTION  m  THOUSANDS  OF  Bin  PER  HOTJB 

FZZT 

100 

200 

300 

400 

500 

750 

1000 

1500 

2000 

20 

4.50 

5.70 

6.60 

7.30 

8.00 

9.40 

10.50 

12.35 

13.85 

40 

4.25 

5.50 

6.40 

7.10 

7.80 

9.15 

10.25 

12.10 

13.55 

60 

4.10 

5.35 

6.20 

6.90 

7.60 

8.90 

10.00 

11.85 

13.25 

80 

4.00 

5.20 

6.00 

6.70 

7.35 

8.65 

9.75 

11.50 

12.85 

100 

3.90 

5.00 

5.90 

6.50 

7.20 

8.40 

9.40 

11.00 

12.40 

gas  requires  the  use  of  highly  efficient  appliances,  the  material  used  for 
the  flue  connection  not  only  should  be  resistant  to  the  corrosion  of  water, 
but  should  resist  the  corrosion  of  dilute  solutions  of  sulphur  trioxide  in 
water.  Local  practice  should  be  followed  in  the  selection  of  the  most 
appropriate  flue  materials. 

When  condensation  in  a  chimney  proves  troublesome,  it  may  be 
necessary  to  provide  a  drain  to  a  dry  well  or  sewer.  The  cause  of  the 
excessive  condensation  should  be  investigated  and  remedied  if  possible. 
This  may  be  done  by  raising  the  flue  temperature  slightly  or  increasing 
the  size  of  the  back-draft  diverten  The  protection  of  unlined  chimneys 
has  been  investigated  and  the  results  indicate  that  after  the  loose  material 
has  been  removed,  the  spraying  with  a  water  emulsion  of  asphalt- 
chromate  provides  an  excellent  protection, 

A  chimney  for  a  gas-fired  boiler  or  furnace  should  be  constructed  in 
accordance  with  the  principles  applicable  to  other  boilers.  Where  the 
wall  forming  a  smoke  flue  is  made  up  of  less  than  an  8-in.  thickness  of 
brick,  concrete,  or  stone,  a  burnt  fire-day  flue  tile  lining  should  be  used. 
Care^  should  be  used  that  the  lengths  of  flue  tile  meet  properly  with  no 
openings  at  the  joints.  Cement  mortar  should  be  used  for  the  entire 
chimney. 

Table  4  gives  the  minimum  cross-sectional  diameters  of  round  chim- 

198 


CHAPTER  10.   CHIMNEYS  AND  DRAFT  CALCULATIONS 

neys  (in  inches)  for  various^  amounts  of  heat  supplied  to  the  appliance, 
and  for  various  chimney  heights.  This  is  in  accordance  with  American 
Gas  Association  recommendations. 


PROBLEMS  IN  PRACTICE 

1  •  What  are  the  principle  factors  influencing  the  intensity  of  natural  draft? 

The  intensity  of  natural  draft  depends  largely  upon  the  height  of  chimney  above  the 
grate  bar  level  and  the  temperature  difference  between  the  chimney  gases  and  the 
atmosphere. 

2  •  What  two  kinds  of  draft  need  he  considered? 

Natural  draft  caused  by  temperature  differences,  and  artificial  draft  caused  by  me- 
chanical forcing. 

3  •  What  is  the  effective  height  of  a  chimney? 

The  height  from  the  grate  level  to  the  top  of  the  chimney  is  the  effective  height  in  pro- 
ducing natural  draft. 

4  •  What  dual  purpose  does  a  tall  chimney  fulfill? 

A  tall  chimney  primarily  creates  the  necessary  draft  to  move  the  air  required  for  the 
combustion  process  and  to  move  the  products  of  combustion,  and  secondarily  it  dis- 
charges the  gases  at  a  high  elevation  to  prevent  them  from  becoming  a  nuisance. 

5  •  What  is  the  direct  influence  of  the  height  on  the  design  of  a  chimney? 

The  immediate  purpose  of  height  is  to  provide  that  draft  intensity  under  the  conditions 
of  chimney  gas  temperature  such  that  it  will  be  adequate  to  overcome  all  the  frictional 
resistances  of  the  installation,  as  well  as  to  provide  for  the  actual  gas  movement. 


6  •  Of  what  importance  is  chimney  cross-sectional  area  in  stack  design? 

The  area  should  be  as  large  as  is  economically  feasible  in  order  that  the  frictional  loss 

for  the  chimney  he 

in  overcoming  the  i 


for  the  chimney  height  should  not  destroy  the  effectiveness  of  the  height-created  draft 
he  necessary  frictional  resistances  of  the  boiler  and  its  flue  connections. 


7  •  Of  what  importance  is  the  Reynolds  number  in  chimney  design? 

It  permits  the  selection  of  a  more  specific  value  of  the  chimney  friction  factor,  rather 
than  a  general  one,  to  correspond  with  conditions  of  size,  nature  of  the  gas,  rate  of  gas 
flow,  and  condition  of  the  surface. 

8  •  a.  Name  the  principle  advantages  of  natural  draft. 

b.  Name  the  principle  disadvantages  of  natural  draft. 

a.  Simplicity,  reliability,  freedom  from  mechanical  parts,  low  cost  of  maintenance, 
relatively  long  life,  relatively  low  depreciation,  operation  with  no  power  requirement. 

b.  Lack  of  flexibility,  irregularity,  dependence  on  surroundings,  susceptibility  to  tem- 
perature changes. 

9  •  How  is  mechanical  draft  created? 

By  forced  draft,  by  induced-draft  fans,  or  by  a  Venturi  chimney. 

10  •  Distinguish  between  theoretical  and  available  draft. 

Theoretical  draft  is  the  difference  in  pressure  inside  and  outside  the  base  of  a  chimney 
when  it  is  under  operating  temperatures  but  when  there  are  no  gases  flowing.  Available 
draft  is  less  than  theoretical  draft  by  the  friction  loss  due  to  the  flow  of  gases  through 
the  chimney. 

199 


HEATING   VENTILATING  AIR  CONDITIONING  GUIDE  1938 

11  •  Explain  the  term  efficiency  of  a  natural  draft  chimney. 

The  efficiency  of  a  chimney  is  the  ratio  of  the  work  it  does  in  moving  gases  to  the  theo- 
retical amount  of  power  it  generates. 

12  •  How  is  the  available  draft  used  in  a  heating  plant? 

The  available  draft  at  the  base  of  the  chimney  is  used  to  overcome  the  loss  in  pressure 
through  the  grate,  the  fuel  bed,  the  boiler  passes,  the  breeching. 

13  •  What  are  some  of  the  factors  that  influence  the  draft  loss  through  the  fuel 
bed? 

Uniformity  and  size  of  coal,  the  amount  of  ash  mixed  with  the  fuel  on  the  grate,  thickness 
of  fuel  bed,  rate  of  combustion,  amount  of  air  supply  as  related  to  the  coal  burning  rate. 

14  •  How  does  the  volatile  matter  content  affect  the  draft  loss  through  the  fuel 
bed? 

The  higher  the  volatile  content  and  the  lower  the  fixed  carbon  content,  the  lower  the 
draft  loss. 

15  •  In  what  cases  will  there  he  no  fuel  bed  draft  loss? 

In  oil,  gas,  and  powdered  fuel  firing  the  fuel  is  mixed  and  burned  in  suspension;  con- 
sequently, no  measurable  resistance  is  encountered  in  the  combustion  zone. 

16  •  Is  it  possible  to  state  an  average  value  for  the  draft  loss  through  a  boiler 
and  its  setting? 

No.  The  draft  loss  varies  widely  and  depends  on  many  factors  such  as  the  size  and  type 
of  gas  passageways.  The  manufacturer  is  usually  able  to  supply  such  information. 

17  •  Of  what  significance  is  the  CDs  content  of  stack  gases  in  establishing 
draft  loss? 

The  COz  content  of  the  exit  gases  is  a  measure  of  the  completeness  of  the  combustion  and 
the  amount  of  excess  air  supplied.  Low  COj  indicates  a  high  excess  of  air  and  hence 
a  high  draft  loss. 

18  •  What  two  effects  does  an  economizer  have  on  the  draft  loss? 

An  economizer  offers  resistance  to  the  flow  of  gases  over  the  added  surfaces;  it  lowers  the 
temperature  of  the  gases  going  to  the  chimney  and  therefore  decreases  the  available 
draft.  This  decrease  often  necessitates  the  addition  of  forced  draft. 

19  •  What  main  provisions  should  be  considered  in  good  chimney  construction? 

Chimneys  should  be  air-tight  and  connected  to  only  one  smoke  opening.  The  chimney 
top  should  be  high  enough  above  surroundings  so  the  wind  will  not  strike  it  at  any  angle 
above  the  horizontal.  ^  Chimney  walls  should  be  not  less  than  one  brick  in  width,  and 
they  should  be  lined  with  fire-clay  tile  of  the  size  required  for  the  attached  heating  unit. 
Tile  lining  sizes  are  stated  as  outside  dimensions;  therefore,  their  effective  dimensions 
are  less  by  the  thickness  of  the  wall. 

20  •  What  is  the  purpose  of  a  back  draft  diverter  as  used  on  gas  burning  units? 

Since  the  fuel  is  supplied  under  pressure  independent  of  draft  it  is  necessary  to  free  the 
unit  from  the  variable  chimney  draft  and  to  supply  air  for  combustion  in  direct  propor- 
tion to  the  supply  of  fuel  gas.  The  back  draft  diverter  protects  the  pilot  and  burners 
from  down  drafts. 


200 


Chapter  11 

AUTOMATIC  FUEL  BURNING  EQUIPMENT 

Classification  of  Stokers,  Combustion  Process  and  Adjustments, 

Furnace  Design,  Classification  of   Oil  Burners,   Combustion 

Chamber  Design,  Classification  of  Gas-Fired  Appliances 

A  UTOMATIC  mechanical  equipment  for  the  combustion  of  solid, 
f\  liquid  and  gaseous  fuels  is  considered  in  this  chapter. 

MECHANICAL  STOKERS 

A  mechanical  stoker  is  a  device  that  feeds  a  solid  fuel  into  a  combustion 
chamber,  provides  a  supply  of  air  for  burning  the  fuel  under  automatic 
control  and,  in  some  cases,  incorporates  a  means  of  removing  the  ash  and 
refuse  of  combustion  automatically.  Coal  can  be  burned  more  efficiently 
by  a  mechanical  stoker  than  by  hand  firing  because  the  stoker  provides  a 
uniform  rate  of  fuel  feed,  better  distribution  in  the  fuel  bed  and  positive 
control  of  the  air  supplied  for  combustion. 

Stokers  may  be  divided  into  four  types  according  to  their  construction, 
namely,  (1)  overfeed  flat  grate,  (2)  overfeed  inclined  grate,  (3)  underfeed 
side  cleaning  type,  and  (4)  underfeed  rear  cleaning  type. 

Overfeed  Flat  Grate  Stokers 

This  type  is  represented  by  the  various  chain-  or  traveling-grate  stokers. 
These  stokers  receive  fuel  at  the  front  of  the  grate  in  a  layer  of  uniform 
thickness  and  move  it  back  horizontally  to  the  rear  of  the  furnace.  Air  is 
supplied  under  the  moving  grate  to  carry  on  combustion  at  a  sufficient 
•rate  to  complete  the  burning  of  the  coal  near  the  rear  of  the  furnace. 
The  ash  is  carried  over  the  back  end  of  the  stoker  into  an  ashpit  beneath. 
This  type  of  stoker  is  suitable  for  small  sizes  of  anthracite  or  coke  breeze 
and  also  for  bituminous  coals,  the  characteristics  of  which  make  it 
desirable  to  bum  the  fuel  without  disturbing  it.  This  type  of  stoker 
requires  an  arch,  over  the  front  of  the  stoker  to  maintain  ignition  of  the 
incoming  fuel.  Frequently,  a  rear  combustion  arch  is  required  to  main- 
tain ignition  until  the  fuel  is  fully  consumed.  A  typical  traveling-grate 
stoker  is  illustrated  in  Fig.  1. 

Another  and  distinct  type  of  overfeed  flat-grate  stoker  is  the 
spreader  (Fig.,  2)  or  sprinkler  type  in  which  coal  is  distributed  either 
mechanically  or  by  air  over  the  entire  grate  surface.  This  type  of  stoker 
has  a  wide  application  on  small  sized  fuels  and  on  certain  special  fuels 
such  as  lignites,  high-ash  coals,  and  coke  breeze. 

201 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


Overfeed  Inclined  Grate  Stokers 

In  general  the  combustion  principle  is  similar  to  the  flat  grate  stoker, 
but  this  stoker  (Fig.  3)  is  provided  with  rocking  grates  set  on  an  incline  to 
advance  the  fuel  during  combustion.  Also  this  type  is  provided  with  an 
ash  plate  where  ash  is  accumulated  and  from  which  it  is  dumped  periodi- 
cally. This  type  of  stoker  is  suitable  for  all  types  of  coking  fuels  but 
preferably  for  those  of  low  volatile  content.  Its  grate  action  has  the 
tendency  to  keep  the  fuel  bed  well  broken  up  thereby  allowing  for  free 


I          I I         T          T 


FIG.  1.    OVERFEED  TRAVELING-GRATE  STOKER 
Coal  conveying  pipe 

^— 

Burner  nozzle 


FIG.  2.   SPREADER  STOKER-PNEUMATIC  TYPE 

passage  of  air.  Because  of  its  agitating  effect  on  the  fuel  it  is  not  so 
desirable  for  badly  clinkering  coals.  Furthermore,  it  should  usually  be 
provided  with  a  front  arch  to  care  for  the  volatile  gases. 

Underfeed  Side  Cleaning  Stokers 

In  this  type  (Fig.  4),  the  fuel  is  introduced  at  the  front  of  the  furnace  to 
one  or  more  retorts,  is  advanced  away  from  the  retort  as  combustion 
progresses,  while  finally  the  ash  is  disposed  of  at  the  sides.  This  type  of 
stoker  is  suitable  for  all  coking  coals  while  in  the  smaller  sizes  it  is  suitable 
for  small  sizes  of  anthracites.  In  this  type  of  stoker  the  fuel  is  delivered 
to  a  retort  beneath  the  fire  and  is  raised  into  the  fire.  During  this  process 

202 


CHAPTER  11.   AUTOMATIC  FUEL  BURNING  EQUIPMENT 

the  volatile  gases  are  released,  are  mixed  with  air,  and  pass  through  the 
fire  where  they  are  burned.  The  ash  may  be  continuously  discharged  as 
in  the  small  stoker  or  may  be  accumulated  on  a  dump  plate  and  periodi- 
cally discharged.  This  stoker  requires  no  arch  as  it  automatically  pro- 
vides for  the  combustion  of  the  volatile  gases. 


Secondary- 


I  fof — Ignited  and  partuHy  coked  fuel 


FIG.  3.   OVERFEED  INCLINED  GRATE  STOKER 


FIG.  4.    UNDERFEED  PLUNGER  TYPE  STOKER 

Underfeed  Rear  Cleaning  Stokers 

This  type  of  stoker  accomplishes  combustion  in  much  the  same  manner 
as  the  side  cleaning  type,  but  consists  of  several  retorts  placed  side  by  side 
and  filling  up  the  furnace  width,  while  the  ash  disposal  is  at  the  rear.  In 
principle,  its  operation  is  the  same  as  the  side  cleaning  underfeed. 

203 


HEATING  VENTILATING  AIR  CONDITIONING   GUIDE  1938 

Stokers  also  may  be  classified  according  to  their  size  based  upon  coal 
feed  rates.  The  following  classification  has  been  made  by  the  United 
States  Department  of  Commerce  in  cooperation  with  the  Stoker  Manu- 
facturers' Association'. 

Class  1.  Up  to  and  including  60  Ib  of  coal  per  hour. 
Class  2.  60  to  100  Ib  of  coal  per  hour. 
Class  3.  100  to  300  Ib  of  coal  per  hour. 
Class  4.  300  to  1200  Ib  of  coal  per  hour. 

(A  fifth  class  is  included  covering  stokers  having  a  feeding  capacity  above  1200  Ib 
of  coal  per  hour). 

Class  1  and  Class  2  Stokers,  Household 

Since  these  stokers  are  used  primarily  for  home  heating,  it  is  desirable 
that  their  design  be  simple  and  attractive  in  appearance,  and  that  they  be 
quiet  and  automatic  in  .operation. 

A  common  type  of  stoker  in  this  class  consists,  essentially  of  a  coal 
reservoir  or  hopper,  a  screw  for  conveying  the  fuel  from  the  hopper  to  the 
burner  head  or  retort;  a  fan  which  supplies  the  air  for  combustion,  a 


FIG.  5.    UNDERFEED  SCREW  STOKER,  HOPPER  TYPE 


transmission  for  driving  the  coal  feed  worm,  and  an  electric  motor  or 
motors  for  supplying  the  motive  power  for  both  coal  feed  and  air  supply 
as  indicated  in  Fig.  5.  The  shape  of  the  retort  in  this  class  of  stokers  is 
usually  round  although  rectangular  retorts  are  favored  by  some  manu- 
facturers. In  all  cases,  however,  the  retort  incorporates  tuyeres  through 
which  the  air  for  combustion  is  admitted. 

Some  household  stokers  are  provided  with  an  automatic  grate-shaking 
mechanism  together  with  screw  conveyors  for  removing  the  ash  from  the 
ashpit  (Fig.  6)  and  depositing  it  in  an  ash  receptacle  outside  the  boiler. 

Certain  types  can  also  be  provided  with  a  coal  conveyor  which  takes 
coal  from  the  storage  bin  and  maintains  a  full  hopper  at  the  stoker.  In 
some  cases  the  coal  bin  functions  as  the  stoker  hopper  as  shown  in  Fig.  7, 
and  an  extended  worm  is  used  to  convey  the  fuel  to  the  combustion  furnace. 
.  Domestic  stokers  may  feed  coal  to  the  furnace  either  intermittently  or 
with  a  continuous  flow  regulated  automatically  to  suit  conditions. 

Household  stokers  are  made  for  ail  classes  of  fuel  ^anthracite,  bitu- 
minous and  semi-bituminous  coals,  and  coke.  The  United  States  Depart- 

204 


CHAPTER  11.   AUTOMATIC  FUEL  BURNING  EQUIPMENT 

went  of  Commerce  has  issued  commercial  standards  for  household  anthra- 
cite burners,  which  may  be  obtained  by  application.  Standards  of 
performance  for  bituminous  coal  stokers  are  also  being  developed  by 
Bituminous  Coal  Research,  Inc.  The  standards  for  anthracite  stokers  are 
described  in  the  next  paragraphs. 

Operating  Requirements  for  Anthracite  Stokers 

Efficiency.  The  over-all  efficiency  of  the  unit  at  all  points  above  50  per  cent  of  maxi- 
mum coal  feed  shall  be  above  50  per  cent  when  installed  in  a  round  sectional  cast-iron 
boiler  having  three  intermediate  sections  and  1H  in.  of  asbestos  insulation  or  its  equiva- 


FIG.  6.    UNDERFEED  SCREW  STOKER  WITH  AUTOMATIC  ASH  REMOVAL 


0    tf 


FIG.  7.    UNDERFEED  SCREW  STOKER,  BIN  FEED  TYPE 


lent  in  good  condition  of  repair,  operating  at  50  per  cent  or  more  of  the  boiler  capacity. 
The  efficiency  shall  be  maintained  for  any  continuous  period  of  4  hours  during  any  test 
or  observation  run. 

Ash  Loss.  Combustible  in  ash  shall  not  exceed  7.5  per  cent  of  the  Btu  content  of  the 
coal  as  fired  at  any  rate  of  coal  feed  above  50  per  cent  of  maximum.  Methods  of  test 
according  to  Code  No.  3  of  the  A.S.H.V.E.1  are  to  be  followed  in  all  details  applicable 
to  stoker  testing. 

Clinker.  Ash  removing  systems  should  at  all  times  be  capable  of  disposing  of  any 
clinker  which  may  be  formed  under  any  conditions  of  operation  with  the  coals  prescribed. 


*A..S.H.V.E.  Performance  Test  Code  for  Steam  Heating  Solid  Fuel  Boilers  (Code  3),  (A.S.H.V.E. 
TRANSACTIONS,  Vol.  35,  1929,  p.  332). 

205 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


Combustion  Rate.  A  combustion  rate  of  at  least  13  Ib  per  square  foot  of  horizontal 
projected  area  of  ash  ring  per  hour  must  be  continuously  maintained  for  at  least  9  hours 
with  the  above  conditions  of  efficiency,  ash  and  clinker. 

Flue  Gas.  Flue  gas  shall  be  not  below  6  per  cent  in  carbon  dioxide  with  a  reasonably 
tight  boiler  at  any  rate  of  operation  above  50  per  cent  of  maximum  coal  feed. 

Maximum  Rating^  The  maximum  rating,  in  terms  of  gross  square  feet  of  water  or 
steam  radiation  which  the  burner  will  supply,  when  intended  for  installation  in  the 
average  existing  cast-iron  boiler,  shall  be  90  per  cent  of  the  maximum  steam  produced  in 
a  round  cast-iron  boiler  in  good  repair  having  three  intermediate  sections  and  the 
equivalent  of  1J£  in.  of  asbestos  insulation.  However,  in  no  case  shall  the  maximum 
rating  be  greater  than  29  sq  ft  of  direct  steam  radiation  for  each  pound  of  coal  fired  per 
hour,  and  in  no  case  shall  ratings  be  based  upon  efficiency  figures  below  50  per  cent. 

The  maximum  rating  as  defined  in  the  preceding  paragraph  shall  be  based  upon  com- 
bustion of  Pennsylvania  anthracite  having  the  following  approximate  analysis: 

Volatile  matter  3.5  to  9  per  cent ;  ash  content  not  to  exceed  15  per  cent ;  sulphur  content 
under  1.5  per  cent;  ash  fusing  temperature  2750  F,  or  above  (volatile,  ash  and  sulphur 
content  on  dry  basis  in  accordance  with  A.S.T.M.  method  D271-33) ;  Btu  content  12,000 
or  above;  properly  sized  as  follows:  A  No.  1  buckwheat  should  pass  through  a  round 
mesh  screen  having  %6  in-  holes  and  over  a  similar  screen  having  5ie  m-  holes.  The 
undersizing  should  not  exceed  15  per  cent  and  the  oversizing  should  not  exceed  10  per 
cent.  A  No.  2  buckwheat  (rice)  should  pass  through  a  round  mesh  screen  having  holes 
5ie  in.  in  diameter  and  over  a  like  screen  having  holes  of  %e  in.  in  diameter.  The  under- 
sizing  should  not  exceed  15  per  cent  and  the  oversizing  should  not  exceed  10  per  cent. 

Coal  Storage.  It  is  recommended  that  the  coal  bin  or  closet  be  constructed  so  as  to 
be  dustproof. 

Electrical  Consumption.  The  electrical  consumption  shall  not  exceed  18  kwh  per 
2000  Ib  of  coal  burned  at  any  rate  of  coal  feed  above  50  per  cent  of  the  maximum. 

Operation  Upon  Other  Sizes  of  Coal.  The  foregoing  specifications  have  been  drafted 
for  operating  with  the  Nos.  1  and  2  buckwheat  sizes  of  anthracite.  In  the  event  that 
other  sizes  are  recommended,  ratings  shall  be  based  upon  the  same  efficiency  and  ash 
loss  requirements. 

Banking.  The  burner  shall  be  so  constructed  or  controlled  as  to  maintain  a  fire 
during  an  indefinite  banking  period. 

Acceleration.  When  the  burner  resumes  operation  after  a  12  hour  banking  period,  the 
time  required  for  the  stack  temperature  to  reach  a  normal  maximum  shall  not  exceed 
60  min. 

Stoker-Fired  Units 

Boilers  and  air  conditioners  especially  designed  for  stokers  are  now 
becoming  available.  Present  designs  feature  better  coordination  between 
the  heat  absorber  and  the  stoker.  Increased  setting  height  and  furnace 
volume  and  more  heating  surface  than  in  conversion  installations  are 
usually  to  be  found  in  these  stoker  units. 

Class  3  Stokers,  Apartment  House,  Small  Commercial 

This  class  is  used  extensively  for  heating  plants  in  apartments  and 
hotels,  and  also  for  small  industrial  plants  such  as  laundries,  bakeries,  and 
creameries.  The  majority  of  stokers  used  in  this  field  are  of  the  underfeed 
type.  The  principal  exception  is  an  overfeed  type  having  step  action 
grates  in  a  horizontal  plane  and  so  arranged  that  they  are  alternately 
moving  and  stationary,  and  are  designed  to  advance  the  fuel  during  com- 
bustion to  an  ash  plate  at  the  rear. 

All  of  the  stokers  are  provided  with  a  coal  hopper  outside  of  the  boiler. 
In  the  underfeed  types,  the  coal  feed  from  this  hopper  to  the  furnace  may 
be  accomplished  by  a  continuously  revolving  screw  or  by  an  intermittent 

206 


CHAPTER  11.   AUTOMATIC  FUEL  BURNING  EQUIPMENT 

plunger.  The  drive  for  the  coal  feed  may  be  an  electric  motor,  or  a  steam 
or  hydraulic  cylinder.  With  an  electric  motor,  the  connection  between 
the  driver  and  the  coal  feed  may  be  through  a  variable  speed  gear  train 
which  provides  two  or  more  speeds  for  the  coal  feed;  or  it  may  be  through 
a  simple  gear  train  and  a  variable  speed  driver  for  the  change  in  speed  of 
the  coal  feed;  or  a  simple  gear  train  with  a  coal  feed  having  an  adjustment 
for  varying  the  travel  of  the  feeding  device.  With  a  steam  or  hydraulic 
cylinder,  the  power  piston  is  connected  directly  to  the  coal  feeding 
plunger. 

The  stokers  in  this  class  vary  also  in  their  retort  design  according  to  the 
fuels  and  load  conditions.  The  retort  is  placed  approximately  in  the 
middle  of  the  furnace  and  is  provided  with  tuyere  openings  at  the  top  on 
all  sides.  In  the  plunger-feed  type  the  retort  extends  from  the  inside  of 
the  front  wall  entirely  to  the  rear  wall  or  to  within  a  short  distance  of  the 
rear  wall.  This  type  of  retort  has  tuyeres  on  the  sides  and  at  the  rear. 

These  stokers  also  differ  in  the  grate  surface  surrounding  the  retort. 
In  many  of  the  worm-feed  stokers  this  grate  is  entirely  a  dead  plate  on 
which  the  fuel  rests  while  combustion  is  completed.  In  the  dead-plate 
type,  all  of  the  air  for  combustion  is  furnished  by  the  tuyeres  at  the  retort. 
Because  of  this,  combustion  is  well  advanced  over  the  retort  so  that  it 
may  easily  be  completed  by  the  air  which  percolates  through  the  fuel  bed. 
With  the  dead-plate  type  of  grate  the  ash  is  removed  through  the  fire 
doors  and  it  is  therefore  desirable  that  the  fuel  used  shall  be  one  in  which 
the  ash  is  readily  reduced  to  a  clinker  at  the  furnace  temperature,  in 
order  that  it  may  be  removed  with  the  least  disturbance  of  the  fuel  bed. 

In  other  stokers  in  this  class,  the  grates  outside  of  the  retort  are  air- 
admitting  and  some  stokers  have  shaking  grates.  These  grates  permit  a 
large  part  of  the  ash  to  be  shaken  into  the  ashpit  beneath,  while  the 
clinkers  are  removed  through  the  fire  doors.  With  this  type  of  grate,  the 
main  air  chamber  extends  only  under  the  retort  while  the  side  grates 
receive  air  by  natural  draft  from  the  ashpit. 

In  still  other  stokers  of  this  class,  the  main  air  chamber  extends  beyond 
the  retort  and  is  covered  with  fuel-bearing,  air-supplying  grates.  With 
this  type  of  grate,  the  fuel  is  supplied  with  air  from  the  main  air  chamber 
throughout  combustion.  Also  with  this  type  of  grate,  dump  plates  are 
provided  beyond  the  grates  where  the  ash  accumulates  and  from  which  it 
can  be  dropped  periodically  into  the  ashpit  beneath. 

Stokers  in  this  class  are  compactly  built  in  order  that  they  may  fit  into 
standard  heating  boilers  and  still  leave  room  for  sufficient  combustion 
space  above  the  grates.  The  height  of  the  grate  is  approximately  the  same 
as  that  of  the  ordinary  grates  of  boilers,  so  that  it  is  usually  possible  to 
install  such  stokers  with  but  minor  changes  in  the  existing  equipment. 
In  some  districts,  there  are  statutory  regulations  governing  such  settings. 

These  stokers  vary  in  furnace  dimensions  from  30  in.  square  to  approxi- 
mately 66  in.  square.  The  capacity  of  the  stokers  is  measured  by  the 
amount  of  coal  that  can  be  burned  per  hour.  In  general,  manufacturers 
recommend  that,  for  continuous  operation,  the  coal  burning  rate  shall  not 
exceed  25  Ib  of  coal  per  square  foot  of  grate  per  hour,  while  for  short 
peaks  this  rate  may  be  increased  to  30  Ib  per  hour.  Although  these 
stokers  were  designed  to  burn  bituminous  coal,  types  are  available  for 

207 


HEATING  VENTILATING   AIR  CONDITIONING   GUIDE  1938 


the  semi-bituminous  coals  such  as  Pocahontas  and  New  River.  They  can 
also  be  used  to  burn  the  small  sizes  of  anthracite  but  at  a  somewhat 
lower  rate. 

Class  4  Stokers,  Medium  Commerial 

These  stokers  are  usually  of  the  screw  feed  type  without  auxiliary 
plungers  or  other  means  of  distributing  the  coal.  Rectangular  retorts 
with  sectional  tuyeres  and  dead  plates  without  air  ports  are  employed. 
The  unit  type  of  construction  is  almost  universally  used,  the  unit  incor- 
porating the  hopper,  the  transmission  for  driving  the  feed  screw,  and  the 
fan  for  supplying  air  for  combustion. 

Class  4  Stokers,  Large  Commercial,  Small  High  Pressure  Plants 

Stokers  in  this  group  vary  widely  in  details  of  mechanical  design  and 
the  several  methods  of  feeding  coal  previously  described  may  be  employed 
Such  methods  of  applying  power  to  the  fuel  conveying  mechanism  as, 
continuous  gear  train  transmission,  ratchet  type  speed  reducer,  hydraulic 
cylinder  and  steam  cylinder  are  used.  Varying  methods  of  ash  disposal 
are  found  in  this  class. 

Large  Stokers 

This  class  includes  stokers  with  hourly  burning  rates  of  over  1200  Ib 
of  coal  per  hour.  The  prevalent  stokers  in  this  field  are : 

a.  Overfeed  flat  grate  stokers. 

b.  Overfeed  inclined  grate  stokers. 

c.  Underfeed  side  cleaning  stokers. 

d.  Underfeed  rear  cleaning  stokers. 

Overfeed  inclined  grate  stokers  are  seldom  built  in  sizes  of  over  500  hp 
and  are  not  as  extensively  used  as  other  types  of  stokers. 

Underfeed  side  cleaning  stokers  are  made  in  sizes  up  to  approximately 
500  hp  and  in  this  field  are  extensively  used.  These  stokers  are  not  so 
varied  in  design  as  those  in  the  smaller  classes  although  the  principle  is 
much  the  same.  Practically  all  of  them  are  of  the  front  coal  feed  type, 
either  power  driven  or  steam  driven.  Dump  plates  at  the  side  are 
manually  operated.  These  stokers  are  heavily  built  and  designed  to 
operate  continuously  at  high  boiler  ratings  with  a  minimum  amount  of 
attention.  Because  of  the  fact  that  all  volatile  gases  must  pass  through  the 
fire  before  reaching  the  combustion  chamber,  these  stokers  will  operate 
smokelessly  under  ordinary  conditions.  Also  because  of  the  fact  that 
these  stokers  are  always  provided  with  forced  draft,  they  are  the  most 
desirable  type  for  fluctuating  loads  or  high  boiler  ratings. 
'  In  the  design  of  the  grates  for  supporting  the  fuel  between  the  retort 
and  the  ash  plates,  the  stokers  differ  in  providing  for  movement  of  the 
fuel  during  combustion.  Some  stokers  are  designed  with  fixed  grates  of 
sufficient  angle  to  provide  for  this  movement  as  the  bed  is  agitated  by  the 
incoming  fuel,  while  others  have  alternate  moving  and  stationary  bars  in 
this  area  and  provide  for  this  movement  mechanically.  In  either  type, 
with  'proper  operation,  all  refuse  will  be  deposited  at  the  dump  plate. 

208 


CHAPTER  11.   AUTOMATIC  FUEL  BURNING  EQUIPMENT 

Recent  developments  in  this  type  of  stoker  provide  for  sliding  distributor 
blocks  along  the  bottom  of  the  retorts  which  give  flexibility  in  providing 
proper  distribution  of  fuel  over  the  grate  area  and  assist  in  preventing 
coke  masses  when  strong  coking  coals  are  used.  Another  difference  in 
these  stokers  is  that  some  use  a  single  air  chamber  under  the  whole  grate 
area  thus  having  the  same  air  pressure  under  the  ignition  area  as  under 
the  rest  of  the  grate,  while  others  have  a  divided  air  chamber  using  the 
full  air  pressure  under  the  ignition  area  and  a  reduced  air  pressure  under 
the  remainder  of  the  grate.  These  stokers  vary  in  size  from  approxi- 
mately 5  sq  ft  to  a  maximum  of  8%  sq  ft. 

The  most  prevalent  type  of  rear  cleaning  underfeed  stoker  is  the 
multiple  retort  design.  Occasionally  double  or  triple  retort  side  cleaning 
underfeeds  are  made.  The  multiple  retort  underfeed  stoker  is  made  for 
the  largest  sizes  of  boilers  for  large  industrial  plants  and  central  stations. 
This  stoker  has  reached  a  very  fine  stage  of  development  mechanically 
and  in  the  matter  of  air  supply  and  control.  In  some  instances  zoned  air 
control  has  been  applied  both  longitudinally  and  transversely  to  the  grate 
surface.  Ash  dumps  on  smaller  sizes  are  sometimes  manually  operated. 

The  Combustion  Process 

Due  to  the  marked  differences  in  design  and  operating  characteristics 
of  stokers  and  the  widely  differing  characteristics  of  stoker  fuels,  it  is 
difficult  to  generalize  on  the  subject  of  combustion  in  automatic  stokers. 

In  anthracite  stokers,  which  are  almost  exclusively  of  the  small  (Class  1) 
underfeed  type,  burning  takes  place  within  the  stoker  retort.  The  ash 
and  refuse  of  combustion  spills  over  the  edge  of  the  retort  into  an  ashpit 
or  receptacle  from  which  it  may  be  removed  either  manually  or  auto- 
matically. Anthracite  is  usually  supplied  for  stoker  firing  in  No.  1 
buckwheat  or  No.  2  buckwheat  size.  Those  stokers  burning  coke  operate 
in  a  similar  manner  to  anthracite  stokers. 

Since  the  majority  of  bituminous  coal  stokers  used  in  heating  plants 
operate  on  the  underfeed  principle  some  general  observations  of  their 
operation  are  given. 

When  the  coal  is  fed  from  the  hopper  or  bin  into  the  retort  it  is  generally 
degraded  to  some  extent  and  some  segregation  of  sizes  occurs.  Because 
of  these  factors  there  may  be  some  difference  in  the  actions  occurring  in  the 
various  portions  of  the  retort. 

The  coal  moving  upward  in  the  retort  toward  the  zone  of  combustion 
established  by  previous  kindling  of  the  fire  is  heated  by  conduction  and 
radiation  from  the  zone  of  combustion.  As  the  temperature  of  the  coal 
rises  it  first  gives  off  moisture  and  occluded  gases,  which  are  largely 
non-combustible.  When  the  temperature  increases  to  around  700  or 
800  F,  the  coal  particles  become  plastic,  the  degree  of  plasticity  varying 
with  the  type  of  coal. 

A  rapid  evolution  of  combustible  volatile  matter  occurs  during  and 
directly  after  the  plastic  stage  of  the  coal.  The  distillation  of  volatile 
matter  continues  above  the  plastic  zone  and  the  coal  is  coked.  The 
strength  and  porosity  of  the  coke  formed  will  vary  according  to  the  size 
and  characteristics  of  the  coal  used. 

209 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

As  more  coal  is  fed  from  below  the  mass  of  coke  continues  to  grow 
forming  a  coke  tree,  plug  or  spar  as  it  is  variously  designated.  After  a 
period  of  time,  dependent  upon  the  strength  of  the  coke  formed,  pieces  of 
the  coke  tree  break  off  and  fall  upon  the  hearth  surrounding  the  retort 
or  within  the  retort  itself  where  they  are  burned. 

While  part  of  the  ash  fuses  into  particles  at  the  surface  of  the  coke  as  it 
is  released,  most  of  it  is  freed  in  unfused  flakes  or  grains.  The  greater 
part  of  this  unfused  ash  remains  on  the  hearth  or  dead  plates  although  a 
part  may  be  expelled  from  the  furnace  with  the  gases. 

The  ash  layer  becomes  thicker  with  time  and  that  near  the  retort,  being 
exposed  to  temperatures  which  are  high  enough  at  times,  fuses  into  a 
clinker.  The  temperature  attained  in  the  fuel  bed,  the  chemical  compo- 
sition and  homogeneity  of  the  ash,  and  the  time  of  heating  are  factors 
which  govern  the  degree  of  fusion. 


FIG.  8.      CROSS-SECTION  OF  FUEL  BED 
WITH  WEAKLY  COKING  COAL 


FIG.  9.      CROSS-SECTION  OF  FUEL  BED 
WITH  STRONGLY  COKING  COAL 


Bituminous  coal  stokers  of  the  Class  1  type  operate  on  the  principle 
of  the  removal  of  ash  as  clinker  and  clinker  tongs  are  provided  to  facilitate 
this  purpose.  Typical  representations  of  underfeed  bituminous  stoker 
fuel  beds  are  shown  in  Figs.  8  and  9. 

The  appearance  of  such  fuel  beds  is  very  ragged  at  times,  and  large 
masses  of  coke  build  up,  surrounded  by  blowholes  with  intense  white 
flame  indicating  the  presence  of  excess  air.  There  is  a  natural  tendency 
for  users  to  disturb  the  fuel  bed  and  make  it  conform  to  the  conventional 
representation  or  ideal  fuel  bed.  Such  attention  should  not  be  required, 
as  usually  the  fuel  bed  tends  to  correct  its  own  faults  as  the  cycles  of 
plasticity,  coke  tree  formation  and  ash  fusion  recur. 

There  are  a  number  of  factors  which  materially  affect  the  rate  and  type 
of  ^ combustion  obtained  in  stoker  usage,  the  most  important  of  these 
being:  the  type  and  design  of  stoker,  the  type  and  characteristics  of  the 
fuel,  the  method  of  stoker  installation  and  the  method  of  stoker  operation. 

210 


CHAPTER  11.   AUTOMATIC  FUEL  BURNING  EQUIPMENT 


Furnace  Design 

The  burning  of  the  fuel  on  the  grate  or  in  the  retort  will  be  influenced 
directly  by  the  stoker  design.  The  burning  of  the  volatile  gases  above  the 
fuel  bed  is  a  matter  of  furnace  design.  Proper  care  should  be  taken  to 
provide  furnaces  sufficiently  liberal  in  volume  and  with  the  grates  or 
retorts  at  a  sufficient  distance  from  the  heating  surface  to  permit  proper 
combustion  of  the  gases.  Smoke  and  low  efficiency  will  result  if  the 
furnace  is  too  small  to  permit  proper  mixing  of  the  gases  and  completion 
of  combustion. 


TABLE  1.    RECOMMENDED  SETTING  HEIGHTS  FOR  HEATING  BOILERS 
EQUIPPED  WITH  MECHANICAL  STOKERS'* 

FIREBOX  BOIUCBS 


Actual  Loadb 

2500 

5000 

7500 

10000 

12500 

15000 

20000  | 

25000 

30000 

A      18" 

18' 

20" 

20" 

22" 

22" 

24"  ! 

24" 

24" 

B 

42" 

48" 

54" 

60" 

66" 

72" 

78"  ; 

84" 

84" 

A  —  Distance  from  bottom  of  Water  Leg  to  floor.  B  m  Distance  from  Crown  Sheet  to  bottom  of  Water  Leg. 

COMPACT  WELDED  BOILERS 


Actual  Loadb 

2500   j   5000   i 

7500 

|  10000  ' 

12500 

15000 

20000 

25000 

30000 

A 

18" 

18" 

20" 

i  20" 

22" 

22" 

24"  '  24" 

24" 

B 

30" 

33"  1 

! 

36" 

:  42"  j 

45" 

48"    54" 

60" 

60" 

A  =  Distance  from  bottom  of  Water  Leg  to  floor.  B  =  Distance  from  Crown  Sheet  to  bottom  of  Water  Leg. 

H.  R.  T.  BOILEBS 


HP 

50 

75  |  100 

125 

150 

i 

175  i  200  i  225 

250 

1 

275    300 

A 

5'-0" 

5'-6"  !  6'-0" 

6'-6" 

7'-0" 

7'-0"  ;  7'-6"  8'-0" 

8'-6" 

9'-0"  9'-0" 

A  =  Distance  from  bottom  of  shell  to  floor. 


Hp  -  Installed  horsepower. 


In  the  case  of  the  Firebox  or  Compact  Welded  type  boilers  the  desired  setting  height  can  be  obtained  by 
combining  A  and  B  dimensions.  The  load  ratings  shown  for  this  class  of  boilers  are  actual  developed  loads 
in  square  feet  of  equivalent  cast-iron  steam  radiation  and  are  not  manufacturers'  ratings. 

The  setting  heights  given  for  H.  R.  T.  boilers  may  be  used  for  developed  loads  up  to  50  per  cent  above 
normal  rating. 

•From  Data  prepared  by  the  Midwest  Stoker  Association. 

bExpressed  as  steam  radiation,  1  sq  ft  =  240  Btu. 

The  standards  that  have  been  most  universally  adopted  for  the  propor- 
tioning of  furnaces  for  bituminous  coal  stokers  are  those  of  the  Midwest 
Stoker  Association  and  the  Steel  Heating  Boiler  Instittite.  See  Chapter  13. 

Table  1  gives  recommended  setting  heights  for  heating  boilers  equipped 
with  mechanical  stokers  using  bituminous  coal. 

Furnace  volume  is  not  an  important  item  in  anthracite  stoker  instal- 
lations. Due  care  should  be  exercised  for  both  anthracite  and  bituminous 
stokers  to  prevent  intense  heat  application  on  the  metal  surfaces  of  the 
combustion  chamber.  The  installation  of  a  baffle  or  adjustment  in  setting 
height  of  the  stoker  may  be  desirable  in  some  cases. 

211 


HEATING   VENTILATING  AIR  CONDITIONING  GUIDE  1938 

The  prime  essentials  of  good  furnace  design  are:  correct  proportions, 
moderate  combustion  rate,  adequate  furnace  volume  and  sufficient  flame 
clearance.  If  these  factors  are  properly  compensated  for  and  provision  is 
made  for  the  proper  mixing  of  the  gases  bituminous  coal  stokers  will 
operate  smokelessly.  In  those  stokers  which  are  operated  intermittently, 
however,  some  smoke  may  be  produced  during  the  off  periods. 

Combustion  Adjustments 

Satisfactory  stoker  performance  may  be  secured  by  regulating  the  coal 
feed  and  the  air  supply  so  as  to  maintain,  as  nearly  as  possible,  an  ideal 
balance  between  the  load  demand  and  the  heat  liberated  by  the  fuel. 
When  the  coal  is  consumed  at  about  the  same  rate  as  that  which  it  is  fed 
this  balance  exists  and  uniform  fuel  bed  conditions  will  be  found.  Under 
such  conditions  no  manual  attention  to  the  fuel  bed  should  be  required 
other  than  the  removal  of  clinker  in  those  stokers  which  operate  on  this 
principle  of  ash  removal. 

Since  complete  combustion  is  not  obtained  in  stoker  furnaces  receiving 
only  the  air  theoretically  required,  it  is  necessary,  even  under  the  best 
of  conditions,  to  supply  from  30  to  50  per  cent  excess  air  to  obtain  desired 
combustion  results.  Due  to  the  variable  characteristics  of  solid  fuels  in 
burning,  consideration  must  be  given  to  a  number  of  factors  which  affect 
the  maintenance  of  the  combustion  conditions  wanted. 

The  specified  rate  of  coal  feed  of  a  stoker  may  vary  due  to  changes  in 
the  bulk  density  of  the  coal  dependent  upon :  (a)  the  size  of  coal,  (6)  dis- 
tribution of  size  in  the  coal,  (c)  segregation  of  coal  in  the  stoker  hopper, 
and  (d)  friability  of  the  coal. 

The  following  factors  may  affect  the  rate  of  air  supply:  (a)  changes  in 
fuel  bed  conditions  and  resistance,  (&)  changes  in  furnace  draft  due  to  a 
variety  of  causes,  i.e.,  changes  in  chimney  draft  because  of  weather 
changes,  seasonal  changes,  back  drafts,  failure  or  inadequacy  of  auto- 
matic draft  regulator,  use  of  chimney  for  other  purposes,  possible  stoppage 
of  the  chimney  and  changes  in  draft  resistance  of  boiler  due  to  partial 
stoppage  of  the  flues,  and  (c)  changes  in  air  inlet  adjustments  to  the  fan. 

Many  domestic  bituminous  stokers  now  incorporate  some  method  of 
automatic  control  which  compensates  for  changes  in  fuel  bed  resistance. 
Since  a  secondary  source  of  air  due  to  leakage  is  present  in  most  installa- 
tions, the  use  of  an  automatic  draft  regulator  to  maintain  the  furnace 
draft  at  about  0.05  in.  of  water  is  desirable.  This  is  quite  important  with 
intermittently  operated  stokers.  Some  fuel  is  burned  by  natural  draft  in 
the  off  periods,  when  fuel  is  not  being  fed,  and  it  is  essential  that  the 
burning  in  these  periods  be  controlled.  With  excessive  draft,  due  either 
to  fan  pressure  or  chimney  pull,  an  increase  in  the  discharge  of  soot  and 
fly  ash  from  the  combustion  chamber  will  result. 

Measurement  of  the  Efficiency  of  Combustion 

As  efficient  combustion  is  based  upon  a  certain  percentage  of  excess  air, 
it  is  possible  to  determine  the  results  by  analysis  of  the  gases  formed  by 
the  combustion  process.  An  Orsat  apparatus  can  be  used  to  determine  the 
percentage  (by  volume)  of  the  carbon  dioxide  (C02),  oxygen  (02)  and 

212 


CHAPTER  11.   AUTOMATIC  FUEL  BURNING  EQUIPMENT 

carbon  monoxide  (CO)  in  the  flue  gases.  Due  to  variations  in  the  fuel  bed 
and  rate  of  burning  of  stoker-fired  .solid  fuels  it  is  not  sufficient  to  analyze 
a  grab  sample.  A  continuous  gas  sample  drawn  at  a  constant  rate  through- 
out an  operating  period  of  reasonably  long  duration  should  be  used. 
A  COz  reading  of  12.5  to  14  per  cent  indicates  that  the  excess  air 
supplied  is  in  the  range  of  30  to  50  per  cent.  The  presence  of  CO  indicates 
a  loss  due  to  improper  mixing  of  the  air  and  the  gases  of  combustion; 
As  an  increase  in  excess  air  maintained  during  on  periods  will  decrease  the 
tendency  toward  smoke  in  the  off  periods  of  intermittently  operated 
bituminous  coal  stokers,  care  should  be  taken  that  the  delivery  of  air  by 
the  fan  is  great  enough  to  avoid  smoke. 

Controls 

The  industry  developed  by  stokers  in  Classes  1,  2,  3  and  4  has  been  due 
as  much  to  the  application  of  proper  controls  as  to  the  stoker  itself.  This 
is  especially  true  of  Class  1  stokers  because  of  their  application  to  resi- 
dential heating,  a  field  wherein  the  majority  of  owners  and  users  are  not 
familiar  with  control  problems  or  stoker  operation. 

The  usual  controls  applied  are  as  follows: 

a.  Thermostats  (plain  and  clock). 

b.  Limit  Controls  (steam,  vapor,  vacuum,  hot  water,  or  air). 

c.  Stack  Temperature  or  Time  Controls  (for  actuating  fires  periodically). 

d.  Relay  (for  low  voltage  controls). 

e.  Safety  or  Overload  Cutout  (for  protection  against  overload). 
/.  Low  Water  Cutout  (steam,  vapor  and  vacuum). 

DOMESTIC  OIL  BURNERS 

An  oil  burner  is  a  mechanical  device  for  producing  heat  automatically 
and  safely  from  liquid  fuels.  This  heat  is  produced  in  the  furnace  or  fire- 
pot  of  hot  water  or  steam  boilers  or  warm  air  furnaces  and  is  absorbed  by 
the  boiler,  and  thus  made  available  for  distribution  to  the  house  through 
the  heating  system. 

With  oil,  as  with  any  kind  of  fuel,  efficient  heat  production  requires  that 
all  combustible  matter  in  the  fuel  shall  be  completely  consumed  and  that 
it  shall  be  done  with  a  minimum  of  excess  air.  The  combustion  of  oil  is  a 
rather  rapid  chemical  reaction.  Excess  air  provides  an  over  supply  of 
oxygen  so  that  all  of  the  oil,  composed  of  carbon  and  hydrogen,  will  be 
completely  oxidized  and  thus  produce  all  the  heat  possible.  The  use  of 
unreasonable  quantities  of  air  in  excess  of  theoretical  combustion  require- 
ments results  in  lowered  efficiencies  due  to  increased  stack  losses.  Such 
losses,  if  not  accompanied  by  unburned  products  of  combustion  (saturated 
and  unsaturated  hydrocarbons,  hydrogen,  etc.),  may  be  offset  somewhat 
by  increasing  the  secondary  heating  surfaces  of  the  heat  absorbing 
medium,  boiler  or  furnace. 

Oil  is  a  highly  concentrated  fuel  composed  mainly  of  hydrogen  and 
carbon.  In  its  liquid  form  oil  cannot  burn.  It  must  be  converted  into  a 
gas  or  vapor  by  some  means.  If  the  excess  air  ^is  to  be  kept  within 
efficient  limits  it  means  that  air  must  be  supplied  in  carefully  regulated 

213 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 

quantities.  The  air  and  oil  vapor  must  be  vigorously  mixed  to  get  a 
rapid  and  complete  chemical  reaction.  The  better  the  mixing,  the  less 
excess  air  that  will  be  needed.  The  combustion  must  take  place  in  a 
space  that  maintains  the  temperatures  high  so  the  reaction  will  not  be 
stopped  before  completion.  When  equipped  with  a  means  of  igniting  the 
oil  and  safety  devices  to  guard  against  mishaps,  the  oil  burner  possesses 
all  of  the  elements  to  be  efficient  and  automatic. 

The  number  of  combinations  of  the  characteristic  elements  of  domestic 
oil  burners  is  rather  large  and  accounts  for  the  variety  of  burners  found  in 
actual  practice.  Domestic  oil  burners  may  be  classified  as  follows: 

1.  AIR  SUPPLY  FOR  COMBUSTION 

a.  Atmospheric — by  natural  chimney  draft. 

b.  Mechanical — electric-motor-driven  fan  or  blower. 

c.  Combination  of  (a)  and  (b) — primary  air  supply  by  fan  or  blower  and  secondary 

air  supply  by  natural  chimney  draft. 

2.  METHOD  OF  OIL  PREPARATION 

a.  Vaporizing — oil  distills  on  hot  surface  or  in  hot  cracking  chamber. 

b.  Atomizing — oil  broken  up  into  minute  globules. 

(1)  Centrifugal — by  means  of  rotating  cup  or  disc. 

(2)  Pressure — by  means  of  forcing  oil  under  pressure  through  a  small 

nozzle  or  orifice. 

(3)  Air  or  steam — by  high  velocity  air  or  steam  jet  in  a  special  type  of 

nozzle. 

(4)  Combination  air  and  pressure — by  air  entrained  with  oil  under  pressure 

and  forced  through  a  nozzle. 

c.  Combination  of  (a)  and  (b). 

3.  TYPE  OF  FLAME 

a.  Luminous — a  relatively  bright  flame.    An  orange-colored  flame  is  usually  best 

if  no  smoke  is  present. 
6.  Non-luminous — Bunsen-type  flame  (i.e.,  blue  flame). 

4.  METHODS  OF  IGNITION 

a.  Electric. 

(1)  Spark — by    transformer    producing    high-voltage    sparks.      Usually 

shielded  to  avoid  radio  interference.    May  take  place  continuously 
while  the  burner  is  operating  or  just  at  the  beginning  of  operation. 

(2)  Resistance — by  means  of  hot  wires  or  plates. 

b.  Gas. 

(1)  Continuous — pilot  light  of  constant  size. 

(2)  Expanding — size  of  pilot  light  expanded  temporarily  at  the  beginning 

of  burner  operation. 

c.  Combination — electric  sparks  light  the  gas  and  the  gas  flame  ignites  the  oil. 

d.  Manual — by  manually-operated  gas  torch  for  continuously  operating  burners. 

5.  MANNER  OF  OPERATION 

a.  On  and  off— burner  operates  only  a  portion  of  the  time  (intermittent). 

b.  High  and  low — burner  operates  continuously  but  varies  from  a  high  to  a  low 

flame. 

c*  Graduated — busner  operates  continuously  but  flame  is  graduated  according  to 
needs  by  regulating  both  air  and  oil  supply. 

214 


CHAPTER  11.   AUTOMATIC  FUEL  BURNING  EQUIPMENT 

A  trade  classification  of  oil  burners  consists  of  the  following  general 
types :  (a)  gun  or  pressure  atomizing,  (&)  rotary  and  (c)  pot  or  vaporizing. 

The  gun  type,  illustrated  in  Fig.  10  is  characterized  by  an  air  tube, 
usually  horizontal,  with  oil  supply  pipe  centrally  located  in  the  tube  and 
arranged  so  that  a  spray  of  atomized  oil  is  introduced  and  mixed  in  the 
combustion  chamber  with  the  air  stream  emerging  from  the  air  tube.  A 
variety  of  patented  shapes  are  employed  at  the  end  of  the  air  tube  to 
influence  the  direction  and  speed  of  the  air  and  thus  the  effectiveness  of 
the  mixing  process. 


-fU*£  BOX  WIL 


FIG.  10.  GUN  TYPE  PRESSURE  ATOMIZING  OIL  BURNER 


FIG.  11.    CENTER  FLAME  VERTICAL 
ROTARY  BURNER 


FIG.  12.   WALL  FLAME  VERTICAL 
ROTARY  BURNER 


The  most  distinguishing  feature  of  vertical  rotary  burners  is  the 
principle  of  flame  application.  These  burners  are  of  two  general  types; 
the  center  flame  and  wall  flame.  In  the  former  type,  (Fig.  11)  the  oil  is 
atomized  by  being  thrown  from  the  rim  of  a  revolving  disc  or  cup  and  the 
flame  burns  in  suspension  with  a  characteristic  yellow  color.  Combustion 
is  supported  by  means  of  a  bowl-shaped  chamber  or  hearth.  The  wall 
flame  burner  (Fig.  12)  differs  in  that  combustion  takes  place  in  a  ring  of 

215 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

refractory  material,  which  is  placed  around  the  hearth.  These  types  of 
burners  are  further  characterized  by  their  installation  within  the  ashpit  of 
the  boiler  or  furnace: 

The  pot  type  burner  (Fig.  13)  can  be  identified  by  the  presence  of  a 
metal  structure,  called  a  pot  or  retort,  in  which  combustion  takes  place. 

When  gun  type  (pressure  atomizing)  or  horizontal  rotary  burners  are 
used  the  combustion  chamber  is  usually  constructed  of  firebrick  or  other 
suitable  refractory  material,  and  is  part  of  the  installation  procedure. 

The  oil  burners  are  operated  by  a  small  electric  motor  which  pumps  the 
oil  and  some  or  all  of  the  air  required.  The  smallest  sizes  can  generally 
burn  not  much  less  than  1  gal  of  oil  per  hour.  The  grade  of  oil  burned 
ranges  from  No.  1  to  No.  4.  No.  4  oil  is  the  heaviest  and  most  viscous  of 
the  various  grades  mentioned.  An  oil  burner  satisfactory  for  No.  4  oil 
can  burn  any  of  the  lighter  grades  easily  but  an  oil  burner  recommended 
for  No..  2  oil  should  never  be  supplied  with  the  heavier  grades.  It  has  been 
found  that  while  the  heavier  grades  of  oil  have  a  smaller  heat  value  per 


FIG.  13.    POT  TYPE  VAPORIZING  BURNER 


pound,  they  have,  due  to  greater  density,  a  larger  heat  value  per  gallon. 
The  relative  economy  of  the  various  grades  must  be  based  upon  price  and 
the  amount  of  excess  air  required  for  clean  and  efficient  combustion. 

Boiler-Burner  Units 

Boilers  and  air  conditioners  especially  designed  for  oil  burners  are 
available  to  the  purchaser  of  this  type  of  equipment.  They  are  used  for 
replacements  as  well  as  for  new  installations.  This  type  of  equipment 
usually  has  more  heating  surface  than  the  older  coal-burning  designs. 
Flue  proportions  and  gas  travel  have  been  changed  with  beneficial  results. 
All  problems  of  combustion  chamber  design,  capacities,  efficiencies,  etc., 
have  been  solved.  The  selection  of  the  proper  size  of  unit  should  be  a 
simple  process. 

COMMERCIAL  OIL  BURNERS 

Liquid  fuels  are  used  for  heating  apartment  buildings,  hotels,  public 
and  office  buildings,  schools,  churches,  hospitals,  department  stores,  as 
well  as  industrial  plants  of  all  kinds.  Contrary  to  domestic  heating,  con- 
venience seldom  is  a  dominating  factor,  the  actual  net  cost  of  heat  pro- 

216 


CHAPTER  11.   AUTOMATIC  FUEL  BURNING  EQUIPMENT 

duction  usually  controlling  the  selection  of  fuel.  Some  of  the  largest  officfc 
buildings  have  been  using  oil  for  many  years.  Many  department  stores 
have  found  that  floor  space  in  basements  and  sub-basements  can  be  used 
to  better  advantage  for  merchandising  wares,  and  credit  the  heat  pro- 
ducing department  with  this  saving. 

Wherever  possible,  the  boiler  plant  should  be  so  arranged  that  either 
oil  or  solid  fuel  can  be  used  at  will,  permitting  the  management  to  take 
advantage  of  changes  in  fuel  costs  if  any  occur.  Each  case  should  be 
considered  solely  in  the  light  of  local  conditions  and  prices. 

Burners  for  commercial  heating  may  be  either  large  models  of  types 
used  in  domestic  heating,  or  special  types  developed  to  meet  the  condi- 
tions imposed  by  the  boilers  involved.  Generally  speaking,  such  burners 
are  of  the  mechanical  or  pressure  atomizing  types,  the  former  using 
rotating  cups  producing  a  horizontal  torch-like  flame.  (Fig.  14).  As  much 


FIG.  14.   HORIZONTAL  ROTATING-CUP  OIL  BURNER 

as  350  gal  of  oil  per  hour  can  be  burned  in  these  units,  and  frequently  they 
are  arranged  in  multiple  on  the  boiler  face,  from  two  to  five  burners  to 
each  boiler. 

The  larger  installations  are  nearly  always  started  with  a^hand  torch, 
and  are  manually  controlled,  but  the  useof  automatic  control  is  increasing, 
and  completely  automatic  burners  are  now  available  to  burn  the  twc 
heaviest  grades  of  oil.  Nearly  all  of  the  smaller  installations,  in  schools, 
churches,  apartment  houses  and  the  like,  are  fully  automatic. 

Because  of  the  viscosity  of  the  heavier  oils,  it  is  customary  to  heat  them 
before  transferring  by  truck  tank,  It  also  has  been  common  practice  to 
preheat  the  oil  between  the  storage  tank  and  the  burner,  as  an  aid  to 
movement  of  the  oil  as  well  as  to  atomization.  This  heating  is  accomplished 
by  heat-transfer  coils,  using  water  or  steam  from  the  heating  boiler,  and 
heating  the  oil  to  within  30  deg  of  its  flash  point. 

Unlike  the  domestic  burner,  units  for  large  commercial  applications 
frequently  consist  of  atomizing  nozzles  or  cups  mounted  on  the  boiler 
front  with  the  necessary  air  regulators,  the  pumps  for  handling  the  oil 

217 


HEATING   VENTUJWING   AIR  CONDITIONING   GUIDE  1938 

and  the  blowers  for  air  supply  being  mounted  in  sets  adjacent  to  the 
boilers.  In  such  cases,  one  pump  set  can  serve  several  burner  units,  and 
common  prudence  dictates  the  installation  of  spare  or  reserve  pump  sets. 
Pre-heaters  and  other  essential  auxiliary  equipment  also  should  be  in- 
stalled in  duplicate. 

Boiler  Settings 

As  the  volume  of  space  available  for  combustion  is  the  determining 
factor  in  oil  consumption,  it  is  general  practice  to  remove  grates  and 
extend  the  combustion  chamber  downward  to  include  or  even  exceed  the 
ashpit  volume;  in  new  installations  the  boiler  should  be  raised  to  make 
added  volume  available.  Approximately  1  cu  ft  of  combustion  volume 
should  be  provided  for  every  developed  boiler  horsepower,  and  in  this 
volume  from  1.5  to  2  Ib  of  oil  can  properly  be  burned.  This  cor- 
responds to  a  maximum  liberation  of  about  38,000  Btu  per  cubic  foot  per 
hour.  There  are  indications  that  at  times  much  higher  fuel  rates  may  be 
satisfactory.  This  in  turn  suggests  that  the  value  of  38,000  Btu  per  cubic 
foot  per  hour  might  be  adjusted  according  to  good  engineering  judgment. 
For  best  results,  care  should  be  taken  to  keep  the  gas  velocity  below  40  ft 
per  second.  Where  checkerwork  of  brick  is  used  to  provide  secondary  air, 

food  practice  calls  for  about  1  sq  in.  of  opening  for  each  pound  of  oil 
red  per  hour.  Such  checkerwork  is  best  adapted  to  flat  flames,  or  to 
conical  flames  that  can  be  spread  over  the  floor  of  the  combustion  chamber. 
The  proper  bricking  of  a  large  or  even  medium  sized  boiler  for  oil  firing  is 
important  and  frequently  it  is  advisable  to  consult  an  authority  on  this 
subject.  The  essential  in  combustion  chamber  design  is  to  provide 
against  flame  impingement  upon  either  metallic  or  fire  brick  surfaces. 
Manufacturers  of  oil  burners  usually  have  available  detailed  plans  for 
adapting  their  burners  to  various  types  of  boilers,  and  such  information 
should  be  utilized. 

The  Combustion  Process 

Efficient  combustion,  as  previously  indicated,  must  produce  a  clean 
flame  and  must  use  relatively  small  excess  of  air,  i.e.,  between  25  and  50 
per  cent.  This  can  be  done  only  by  vaporizing  the  oil  quickly,  completely, 
and  mixing  it  vigorously  with  air  in  a  combustion  chamber  hot  enough 
to  support  the  combustion.  A  vaporizing  burner  prepares  the  oil,  for 
combustion,  by  transforming  the  liquid  fuel  to  the  gaseous  state  through 
the  application  of  heat.  This  is  accomplished  before  the  oil  vapor  mixes 
with  air  to  any  extent  and  if  the  air  and  oil  vapor  temperatures  are  high 
and  the  fire  pot  hot,  a  clear  blue  flame  is  produced.  There  may  be  a 
deficiency  of  air  as  shown  by  the  presence  of  carbon  monoxide  (CO)  or 
an  excessive  supply  of  air,  depending  upon  burner  adjustment,  without 
altering  the  clean,  blue  appearance  of  the  flame. 

An  atomizing  burner  i.e.,  gun  and  rotary  types  is  so  named  because  the 
oil  is  mechanically  separated  into  very  fine  particles  so  that  the  surface 
exposure  of  the  liquid  to  the  radiant  heat  of  the  combustion  chamber  is 
vastly  increased  and  vaporization  proceeds  quickly.  The  result  of  such 
practice  is  the  ability  to  burn  more  and  heavier  oil  within  a  given  com- 
bustion space  or  furnace  volume.  Since  the  air  enters  the  fire  pot  with  the 
liquid  fuel  particles,  it  follows  that  mixing,  vaporization  and  burning  are 

218 


CHAPTER  11.   AUTOMATIC  FUEL  BURNING  EQUIPMENT 

all  occurring  at  once  in  the  same  space.  This  produces  a  luminous 
instead  of  a  blue  or  non-luminous  flame.  In  this  case  a  deficient  amount 
of  air  is  indicated  by  a  dull  red  or  dark  orange  flame  with  smoky  flame  tips. 

An  excessive  supply  of  air  may  produce  a  brilliant  white  flame  in  some 
cases  or,  in  others,  a  short  ragged  flame  with  incandescent  sparks  flashing 
through  the  combustion  space.  While  extreme  cases  may  be  easily 
detected,  it  is  generally  not  possible  to  distinguish,  by  the  eye  alone,  the 
finer  adjustment  which  competent  installation  requires. 

Certain  tests  indicate  that  there  is  no  difference  in  economy  between  a 
blue  flame  and  a  luminous  flame  if  the  position,  shape  and  the  per  cent  of 
excess  air  of  both  flames  are  about  the  same. 

Furnace  or  Combustion  Chamber  Design 

The  furnace  or  combustion  chamber  may  be  defined  as  that  part  of  a 
boiler  or  conditioner  in  which  combustion  is  established.  With  burners 
requiring  a  refractory  combustion  chamber  the  size  and  shape  should  be  in 
accordance  with  the  manufacturer's  instructions.  It  is  important  that 
the  chamber  shall  be  as  nearly  air  tight  as  is  possible,  except  when  the 
particular  burner  requires  a  secondary  supply  of  air  for  combustion. 

It  is  evident  that  the  atomizing  burner  is  dependent  upon  the  surround- 
ing heated  refractory  or  fire  brick  surfaces  to  vaporize  the  oil  and  support 
combustion.  While  the  importance  of  the  combustion  chamber  is  obvious, 
its  design  has  been  troublesome.  Unsatisfactory  combustion  may  be  due 
to  inadequate  atomization  and  mixing.  A  combustion  chamber  can  only 
compensate  for  these  things  to  a  limited  extent.  If  liquid  fuel  continually 
reaches  some  part  of  the  fire  brick  surface,  a  carbon  deposit  will  result. 
Fundamentally,  the  combustion  chamber  should  enclose  a  space  having  a 
shape  similar  to  the  flame  but  large  enough  to  avoid  flame  contact. 
The  nearest  approach  in  practice  is  to  have  the  bottom  of  the  combustion 
chamber  flat  but  far  enough  below  the  nozzle  to  avoid  flame  contact, 
the  sides  tapering  from  the  air  tube  at  the  same  angle  as  the  nozzle  spray 
and  the  back  wall  rounded.  A  plan  view  of  the  combustion  chamber  thus 
resembles  in  shape  the  outline  of  the  flame.  In  this  way  as  much  fire  brick 
as  possible  is  close  to  the  flame  so  it  may  be  kept  quite  hot.  This  insures 
quick  vaporization,  rapid  combustion  and  better  mixing  by  eliminating 
dead  or  inactive  spaces  in  the  combustion  chamber.  An  overhanging 
arch  at  the  back  of  the  fire  pot  is  sometimes  used  to  increase  the  flame 
travel  and  give  more  time  for  mixing  and  burning  and  sometimes  to  pre- 
vent the  gases  from  going  too  directly  into  the  boiler  flues.  When  good 
atomization  and  vigorous  mixing  are  achieved  by  the  burner,  combustion 
chamber  design  becomes  a  less  critical  matter.  Where  secondary  air  is 
used,  combustion  chamber  design  is  quite  important.  With  some  of  the 
vertical  rotary  burners  considerable  care  must  be  exercised  in  definitely 
following  the  manufacturers  instructions  when  installing  the  hearth  as 
in  this  class  successful  performance  depends  upon  this  factor. 

Combustion  Adjustments 

Where  adjustments  of  oil  and  air  have  been  made  which  give  efficient 
combustion,  the  problem  of  maintaining  the  adjustments  constant  be- 
comes an  important  one.  Particularly  is  this  true  when  the  change 
causes"  the  per  cent  of  excess  air  to  decrease  below  allowable  limits  of  the 

219 


HEATING  VENTILATING   AIR  CONDITIONING  GUIDE  1938 

burner.  A  decrease  in  air  supply  while  the  oil  delivery  remains  constant 
or  an  increase  in  oil  delivery  while  the  air  supply  remains  constant  will 
make  the  mixture  of  oil  and  air  too  rich  for  clean  combustion.  The  more 
efficient  the  adjustment  (i.e.,  25  per  cent  excess  air)  the  more  critical  it 
will  be  of  variations.  The  oil  and  air  supply  rates  must  remain  constant. 

The  following  factors  may  influence  the  oil  delivery  rate:  (a)  changes 
in  oil  viscosity  due  to  temperature  change  or  variations  in  grade  of  oil 
delivered,  (6)  erosion  of  atomizing  nozzle,  (c)  fluctuations  in  by-pass  relief 
pressures  and  (d)  possible  variations  in  methods  2b  (3)  and  2b  (4)  listed  in 
the  previous  classification  table.  Note  that  any  change  due  to  partial 
stoppage  of  oil  delivery  will  increase  the  proportion  of  excess  air.  This 
will  result  in  less  heat,  reduced  economy  and  possibly  a  complete  inter- 
ruption of  service  but  usually  no  soot  will  form. 

The  following  factors  may  influence  the  air  supply:  (a)  changes  in 
combustion  draft  due  to  a  variety  of  causes  (i.e.,  changes  in  chimney 
draft  because  of  weather  changes,  seasonal  changes,  back  drafts,  failure 
or  inadequacy  of  automatic  draft  regulator,  use  of  chimney  for  other 
purposes,  possible  stoppage  of  the  chimney  and  changes  in  draft  resis- 
tance of  boiler  due  to  partial  stoppage  of  the  flues),  and  (6)  changes  in  air 
inlet  adjustments  to  the  fan. 

It  is  recognized  that  a  secondary  source  of  air  due  to  leakage  in  the 
boiler  setting  is  present  in  many  installations  and  it  is  highly  desirable  that 
this  leakage  be  reduced  to  a  minimum.  Obviously  the  amount  of  air 
leakage  will  be  determined  by  the  draft  in  the  combustion  chamber. 
It  is  important  that  this  draft  should  be  reduced  as  low  as  is  consistent 
with  the  proper  disposal  of  the  gases  of  combustion.  When  using  mechani- 
cal draft  burners  with  average  conditions,  the  combustion  chamber  draft 
should  not  be  allowed  to  exceed  0.02-0.05  in.  water.  An  automatic  draft 
regulator  is  very  helpful  in  maintaining  such  values, 

Measurement  of  the  Efficiency  of  Combustion. 

Efficient  combustion  being  based  upon  a  clean  flame  and  certain 
proportions  of  oil  and  air  employed,  it  is  possible  to  determine  the  results 
by  analyzing  the  gases  formed  by  the  combustion  process.  An  Orsat 
apparatus  is  a  device  which  measures  the  volume  of  carbon  dioxide 
(C02),  oxygen  (0%)  and  carbon  monoxide  (CO)  in  the  flue  gases.  Except 
in  the  case  of  a  non-luminous  flame  it  is  usually  sufficient  to  analyze  only 
for  carbon  dioxide  (CO*).  A  showing  of  10  to  12  per  cent  indicates  the 
best  adjustment  if  the  flame  is  clean.  Most  of  the  good  installations  at 
the  present  time  show  from  8  to  10  per  cent  COg.  Taking  into  account 
the  potential  hazard  of  oil  or  air  fluctuations  with  low  excess  air  (high 
CO*)  a  setting  to  give  10  per  cent  COz  constitutes  a  reasonable  standard 
for  most  oil  burners.  This  is  particularly  true  of  non-luminous  flame 
burners  which  will  not  function  properly  with  less  than  10  per  cent  COa. 

Controls 

Oil  burner  controls  may  be  divided  into  two  parts:  (a)  devices  to 
regulate  burner  operation  so  the  desired  house  heating  result  may  be 
obtained  and  (&)  devices  for  the  safety  and  protection  of  the  boiler  and 
burner.  For  control  devices  generally  consult  Chapter  37.  The  room 
thermostat  has  recently  been  improved  to  provide  more  frequent  burner 

220 


CHAPTER  11.   AUTOMATIC  FUEL  BURNING  EQUIPMENT 

operation  and  greater  uniformity'  of  room  temperature.  Class  (b)  controls 
comprises  a  device  to  shut  off  the  burner  if  the  oil  fails  to  ignite  or  if  the 
flame  should  cease  due  to  lack  of  oil;  a  device  actuated  by  steam  boiler 
pressure  to  shut  off  the  burner  when  the  pressure  reaches  some  pre- 
determined value;  a  device  on  the  boiler  to  shut  off  the  burner  if  the  water 
level  acts  too  low  for  safety  or  one  which  automatically  feeds  additional 
water  to  the  boiler;  a  device  on  warm  air  furnaces  to  shut  off  the  burner  if 
the  air  temperature  gets  too  high;  a  valve  in  the  oil  supply  line  which 
automatically  closes  in  the  event  of  fire  in  or  near  the  cellar;  and  a  device 
to  keep  the  temperature  of  the  boiler  water  within  certain  limits  when  it  is 
being  used  to  heat  domestic  hot  water.  These  devices  are  all  tested  and 
approved  by  the  Underwriters'  Laboratory  of  Chicago,  111.,  before  they 
are  offered  to  the  purchaser.  The  selection  of  class  (&)  devices  is  made  by 
the  oil  burner  manufacturer. 

Fuel  Oil  Gages 

To  insure  a  constant  supply  of  fuel  oil  and  to  check  deliveries  and 
consumption  it  is  essential  to  have  accurate  means  of  readily  determining 
the  quantity  of  oil  in  the  storage  tank.  For  this  purpose  various  types  of 
indicating  or  recording  gages  are  used,  the  simplest  forms  being  the  glass 
level  gage,  and  a  float-and-dial  arrangement  having  a  graduated  dial  face 
indicating  the  proportion  of  the  tank  containing  liquid.  Other  more 
accurate  and  dependable  devices  are  designed  to  operate  by  hydraulic 
action  or  by  hydrostatic  impulse.  These  instruments  may  be  attached  to 
the  tank,  giving  a  direct  reading  of  the  liquid  contents;  or  the  instrument 
itself  may  be  located  at  a  convenient  point  remote  from  the  tank  and 
connected  with  the  tank  by  pipe  or  tubing.  The  quantity  readings  may 
be  in  gallons  of  liquid,  height  of  liquid  level  in  feet  and  inches,  or  in  other 
desired  units  of  measurement. 

GAS-FIRED  APPLIANCES 

The  increased  use  of  gas  for  house  heating  purposes  has  resulted  in  the 
production  of  such  a  large  number  of  different  types  of  gas  heating 
systems  and  appliances  that  today  there  is  probably  a  greater  variety  of 
them  than  there  is  for  any  other  kind  of  fuel. 

Gas-fired  heating  systems  may  be  classified  as  follows : 

I.    Gas-Designed  Heating  Systems. 

A.  Central  Heating  Plants. 

1.  Steam,  hot  water,  and  vapor  boilers. 

2.  Warm  air  furnaces. 

B.  Unit  Heating  Systems. 

1.  Warm  air  floor  furnaces. 

2.  Industrial  unit  heaters. 

3.  Space  heaters. 

4.  Garage  heaters. 

II.    Conversion  Heating  Systems. 
A,  Central  Heating  Plants. 

1.  Steam,  hot  water  and  vapor  boilers. 

2.  Warm  air  basement  furnaces. 

221 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 

These  systems  are  supplied  with  either  automatic  or  manual  control. 
Central  heating  plants,  for  example,  whether  gas  designed  or  conversion 
systems,  may  be  equipped  with  room  temperature  control,  push-button 
control,  or  manual  control. 

Gas-Fired  Boilers 

Information  on  gas-fired  boilers  will  be  found  in  Chapter  13.  Either 
snap  action  or  throttling  control  is  available  for  gas  boiler  operation. 
This  is  especially  advantageous  in  straight  steam  systems  because  steam 
pressures  can  be  maintained  at  desired  points,  while  at  the  same  time 
complete  cut-off  of  gas  is  possible  when  the  thermostat  calls  for  it. 

Gas-Fired  Warm  Air  Furnaces 

Warm  air  furnaces  are  variously  constructed  of  cast  iron,  sheet  metal 
and  combinations  of  the  two  materials.  If  sheet  metal  is  used,  it  must 
be  of  such  a  character  that  it  will  have  the  maximum  resistance  to  the 
corrosive  effect  of  the  products  of  combustion.  With  some  varieties  of 
manufactured  gases,  this  effect  is  quite  pronounced.  Warm  air  furnaces 
are  obtainable  in  sizes  from  those  sufficient  to  heat  the  largest  residence 
down  to  sizes  applicable  to  a  single  room.  The  practice  of  installing  a 
number  of  separate  furnaces  to  heat  individual  rooms  is  peculiar  to  mild 
climates.  Small  furnaces,  frequently  controlled  by  electrical  valves 
actuated  by  push-buttons  in  the  room  above,  are  often  installed  to  heat 
rooms  where  heat  may  be  desired  for  an  hour  or  so  each  day.  These 
furnaces  are  used  also  for  heating  groups  of  rooms  in  larger  residences. 
In  a  system  of  this  type  each  furnace  should  supply  a  group  of  rooms  in 
which  the  heating  requirements  for  each  room  in  the  group  are  similar  as 
far  as  the  period  of  heating  and  temperature  to  be  maintained  are  con- 
cerned. 

The  same  fundamental  principle  of  design  that  is  followed  in  the  con- 
struction of  boilers,  that  is,  breaking  the  hot  £as  into  fine  streams  so  that 
all  particles  are  brought  as  close  as  possible  to  the  heating  surface,  is 
equally  applicable  to  the  design  of  warm  air  furnaces. 

Codes  for  proportioning  warm  air  heating  plants,  such  as  that  formu- 
lated by  the  National  Warm  Air  Heating  and  Air  Conditioning  Association 
are  equally  applicable  to  gas  furnaces  and  coal  furnaces.  Recirculation 
should  always  be  practiced  with  gas-fired  warm  air  furnaces.  It  not  only 
aids  in  heating,  but  is  essential  to  economy.  Where  fans  are  used  in  con- 
nection with  warm  air  furnaces  for  residence  heating,  it  is  well  to  have  the 
control  of  the  fan  and  of  the  gas  so  coordinated  that  there  will  be  sufficient 
delay  between  the  turning  on  of  the  gas  and  the  starting  of  the  fan  to 
prevent  blasts  of  cold  air  being  blown  into  the  heated  rooms.  An  additional 
thermostat  in  the  air  duct  easily  may  be  arranged  to  accomplish  this. 

Floor  Furnaces 

Warm  air  floor  furnaces  are  well  adapted  for  heating  first  floors,  or 
where  heat  is  required  in  only  one  or  two  rooms.  A  number  may  be  used 
to  provide  heat  for  the  entire  building  where  all  rooms  are  on  the  ground 
floor,  thus  giving  the  heating  system  flexibility  as  any  number  of  rooms 
may  be  heated  without  heating  the  others.  With  the  usual  type  the 
register  is  installed  in  the  floor,  the  heating  element  and  gas  piping  being 

222 


CHAPTER  11.   AUTOMATIC  FUEL  BURNING  EQUIPMENT 

suspended  below.  Air  is  taken  downward  between  the  two  sheets  of  the 
double  casing  and  discharged  upward  over  the  heating  surfaces  and  into 
the  room.  The  appliance  is  controlled  from  the  room  to  be  heated  by 
means  of  a  control  lever  located  near  the  edge  of  the  register.  The  handle 
of  the  control  is  removable  as  a  precaution  against  accidental  turning 
on  or  off  of  the  gas  to  the  furnace. 

Space  Heaters 

Space  heaters  are  generally  used  for  auxiliary  heating,  but  may  be,  and 
are  in  many  cases,  installed  for  furnishing  heat  to  entire  buildings.  With 
the  exception  of  wall  heaters,  they  are  portable,  and  can  be  easily  removed 
and  stored  during  the  summer  season.  Although  they  should  be  connected 
with  solid  piping  it  is  sometimes  desirable  to  connect  them  with  flexible 
gas  tubing  in  which  case  a  gas  shut-off  on  the  heater  is  not  permitted,  and 
only  A.G.A.  approved  tubing  should  be  used. 

Parlor  furnaces  or  circulators  are  usually  constructed  to  resemble  a 
cabinet  radio.  They  heat  the  room  entirely  by  convection,  i.e.,  the  cold 
air  of  the  room  is  drawn  in  near  the  base  and  passes  up  inside  the  jacket 
around  a  drum  or  heating  section,  and  out  of  the  heater  at  or  near  the  top. 
These  heaters  cause  a  continuous  circulation  of  the  air  in  the  room  during 
the  time  they  are  in  operation.  The  burner  or  burners  are  located  in  the 
base  at  the  bottom  of  an  enclosed  combustion  chamber.  The  products  of 
combustion  pass  up  around  baffles  within  the  heating  element  or  drum, 
and  out  the  flue  at  the  back  near  the  top.  They  are  well  adapted  not  only 
for  residence  room  heating  but  also  for  stores  and  offices. 

Radiant  heaters^  make  admirable  auxiliary  heating  appliances  to  be  used 
during  the  occasional  cool  days  at  the  beginning  and  end  of  the  heating 
season  when  heat  is  desired  in  some  particular  room  for  an  hour  or  two. 
The  radiant  heater  gives  off  a  considerable  portion  of  its  heat  in  the  form 
of  radiant  energy  emitted  by  an  incandescent  refractory  that  is  heated  by 
a  Bunsen  flame.  They  are  made  in  numerous  shapes  and  designs  and  in 
sizes  ranging  from  two  to  fourteen  or  more  radiants.  Some  have  sheet- 
iron  bodies  finished  in  enamel  or  brass  while  others  have  cast-iron  or  brass 
frames  with  heavy  fire-clay  bodies.  An  atmospheric  burner  is  supported 
near  the  center  of  the  base,  usually  by  set  screws  at  each  end.  Others 
have  a  group  of  small  atmospheric  burners  supported  on  a  manifold 
attached  to  the  base.  Most  radiant  heaters  are  supported  on  legs  and  are 
portable;  however,  there  are  also  types  which  are  encased  in  a  jacket 
which  fits  into  the  wall  with  a  grilled  front,  similar  to  the  ordinary  wall 
register.  Others  are  encased  in  frames  which  fit  into  fireplaces. 

Gas-fired  steam  and  hot  water  radiators  are  popular  types  of  room  heating 
appliances.  They  provide  a  form  of  heating  apparatus  for  intermittently 
heated  spaces  such  as  stores,  small  churches  and  some  types  of  offices  and 
apartments.  They  are  made  in  a  large  variety  of  shapes  and  sizes  and  are 
similar  in  appearance  to  the  ordinary  steam  or  hot  water  radiator  con- 
nected to  a  basement  boiler.  A  separate  combustion  chamber  is  provided 
in  the  base  of  each  radiator  and  is  usually  fitted  with  a  one-piece  burner. 
They  may  be  secured  in  either  the  vented  or  unvented  types,  and  with 
steam  pressure,  thermostatic  or  room  temperature  controls. 

Warm  air  radiators  are  similar  in  appearance  to  the  steam  or  hot  water 
radiators.  They  are  usually  constructed  of  pressed  steel  or  sheet  metal 

223 


HEATING  VENTILATING   AIR  CONDITIONING  GUIDE  1938 

hollow  sections.  The  hot  products  of  combustion  circulate  through  the 
sections  and  are  discharged  out  a  flue  or  into  the  room,  depending  upon 
whether  the  radiator  is  of  the  vented  or  unvented  type. 

Garage  heaters  are  usually  similar  in  construction  to  the  cabinet 
circulator  space  heaters,  except  that  safety  screens  are  provided  over  all 
openings  into  the  combustion  chamber  to  prevent  any  possibility  of 
explosion  from  gasoline  fumes  or  other  gases  which  might  be  ignited  by 
an  open  flame.  They  are  usually  provided  with  automatic  room  tem- 
perature controls  and  are  well  suited  for  heating  either  residence  or 
commercial  garages, 

Conversion  Burners 

Residence  heating  with  gas  through  the  use  of  conversion  burners  in- 
stalled in  coal-designed  boilers  and  furnaces  represents  a  common  type 
of  gas-fired  house  heating  system.  In  many  conversion  burners  radiants 
or  refractories  are  employed  to  convert  some  of  the  energy  in  the  gas  to 
radiant  heat.  Others  are  of  the  blast  type,  operating  without  refractories. 

Many  conversion  units  are  equipped  with  sheet  metal  secondary  air 
ducts  which  are  inserted  through  the  ashpit  door.  The  duct  is  equipped 
with  automatic  air  controls  which  open  when  the  burners  are  operating 
and  close  when  the  gas  supply  is  turned  off.  This  prevents  a  large  part 
of  the  circulation  of  cold  air  through  the  combustion  space  of  the  ap- 
pliance when  not  in  operation.  By  means  of  this  duct  the  air  necessary 
for  proper  combustion  is  supplied  directly  to  the  burner,  thereby  making 
it  possible  to  reduce  the  amount  of  excess  air  passing  through  the  com- 
bustion chamber. 

Conversion  units  are  made  in  many  sizes  both  round  and  rectangular 
to  fit  different  types  and  makes  of  boilers  and  furnaces.  They  may  be 
secured  with  manual,  push-button,  or  room  temperature  control. 

The  Combustion  Process 

*  Because  of  the  varying  composition  of  gases  used  for  domestic  heating 
it  is  difficult  to  generalize  on  the  subject  of  gas  burner  combustion. 
Refer  to  the  section  on  Gas  Classification,  in  Chapter  9. 

Combustion  Adjustments 

Little  difficulty  should  be  experienced  in  maintaining  efficient  com- 
bustion conditions  when  burning  gas.  The  fuel  supply  is  normally  held 
to  close  limits  of  variation  in  pressure  and  calorific  value  and,  therefore, 
the  rate  of  heat  supply  is  nominally  constant.  Since  the  force  necessary  to 
introduce  the  fuel  into  the  combustion  chamber  is  an  inherent  factor  of 
the  fuel,  no  draft  by  the  chimney  is  required  for  this  purpose.  The  use  of  a 
draft  diverter  insures  the  maintenance  of  constant  low  draft  condition  in 
the  combustion  chamber  with  a  resultant  stability  of  air  supply.  A  draft 
diverter  is  also  helpful  in  controlling  the  amount  of  excess  air  and  pre- 
venting back  drafts  which  might  extinguish  the  flame. 

Measurement  of  the  Efficiency  of  Combustion 

It  is  possible  to  determine  the  results  of  combustion  by  analyzing  the 
gases  of  combustion  with  an  Orsat  apparatus.  It  is  desirable  to  determine 

224 


CHAPTER  11.   AUTOMATIC  FUEL  BURNING  EQUIPMENT 

the  percentage  of  carbon  dioxide  (C02),  oxygen  (02)  and  carbon  monoxide 
(CO)  in  the  flue  gases.  While  ultimate  COz  values  of  10  to  12  per  cent  may 
be  obtained  from  the  combustion  of  gases  commonly  used  for  domestic 
heating,  a  combustion  adjustment  which  will  show  from  8  to  10  per  cent 
C0a  represents  a  practical  value.  Under  normal  conditions  no  CO  will  be 
produced  by  a  gas-fired  boiler  or  furnace.  Limitations  as  to  output  rating 
by  the  A.G.A.  are  based  upon  operation  with  not  more  than  0.04  per  cent 
CO  in  the  products  of  combustion.  This  is  too  small  an  amount  to  be 
determined  by  the  ordinary  flue  gas. analyzer. 

Controls 

Gas  burner  controls  may  be  divided  into  two  parts:  (a)  devices  to 
regulate  burner  operation  so  that  the  desired  house  heating  results  may  be 
obtained  and  (b)  devices  for  the  safety  of  the  boiler  and  burner.  Control 
devices  are  treated  in  detail  in  Chapter  37.  A  room  thermostat  may  be 
used  as  a  control  of  house  heating  effect.  These  may  be  obtained  in  a 
number  of  types.  Some  central  heating  plants  are  equipped  with  push- 
button or  manual  control.  Class  (&)  controls  include  a  device  to  shut  off 
the  burner  if  the  gas  fails  to  ignite,  a  device  actuated  by  boiler  pressure, 
water  temperature,  or  furnace  bonnet  temperature  to  shut  off  the  burner 
when  the  pressure  or  temperature  becomes  excessive,  a  device  on  the 
boiler  to  shut  off  the  burner  if  the  water  level  falls  below  safe  limits  or  one 
which  automatically  feeds  additional  water  to  the  boiler,  and  a  device  for 
controlling  the  gas  pressure  within  desired  limits.  The  main  gas  valve 
may  be  either  of  the  snap  action  or  throttling  type. 

Sizing  Gas-Fired  Heating  Plants 

While  gas-burning  equipment  can  be  and  usually  is  so  installed  as  to  be 
completely  automatic,  maintaining  the  temperature  of  rooms  at  a  pre- 
determined and  set  figure,  there  are  in  use  installations  which  are  manually 
controlled.  Experience  has  shown  that,  in  order  to  effectively  overcome 
the  starting  load  and  losses  in  piping,  a  manually-controlled  gas  boiler 
should  have  an  output  as  much  as  100  per  cent  greater  than  the  equiva- 
lent standard  cast-iron  column  radiation  which  it  is  expected  to  serve. 

Boilers  under  thermostatic  control,  however,  are  not  subject  to  suclr 
severe  pick-up  or  starting  loads.  Consequently,  it  is  possible  to  use  $ 
much  lower  selection,  or  safety  factor.  A  gas-fired  boiler  under  thermo 
static  control  is  sensitive  to  variations  in  room  temperatures  so  that  ii 
most  cases  a  factor  of  20  per  cent  is  sufficient  for  pick-up  load. 

The  factor  to  be  allowed  for  loss  of  heat  from  piping,  however,  mus 
vary  somewhat,  the  proportionate  amount  of  piping  installed  being  con 
siderably  greater  for  small  installations  than  for  large  ones.  Consequent! 
a  selection  factor  for  thermostatically  controlled  boilers  must  be  variable 
Liberal  selection  factors  to  be  added  to  the  installed  steam  radiatio 
under  thermostatic  control  are  given  in  Fig.  3  of  Chapter  13. 

Appliances  used  for  heating  with  gas  should  bear  the  approval  seal  < 
the  American  Gas  Association  Testing  Laboratory.  Installations  shoul 
be  made  in  accordance  with  the  recommendations  shown  in  the  publ 
cations  of  that  association. 

225 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

Ratings  for  Gas  Appliances 

Since  a  gas  appliance  has  a  heat-generating  capacity  that  can  be  pre- 
dicted accurately  to  within  1  or  2  per  cent,  and  since  this  capacity  is  not 
affected  by  such  things  as  condition  of  fuel  bed  and  soot  accumulation, 
makers  of  these  appliances  have  an  opportunity  to  rate  their  product  in 
exact  terms.  Consequently  all  makers  give  their  product  an  hourly  Btu 
output  rating.  This  is  the  amount  of  heat  that  is  available  at  the  outlet  of 
a  boiler  in  the  form  of  steam  or  hot  water,  or  at  the  bonnet  of  the  furnace 
in  the  form  of  warm  air.  The  output  rating  is  in  turn  based  upon  the 
Btu  input  rating  which  has  been  approved  by  the  American  Gas  Asso- 
ciation Testing  Laboratory  and  upon  an  average  efficiency  which  has 
been  assigned  by  that  association. 

In  the  case  of  boilers,  the  rating  can  be  put  in  terms  of  square  feet  of 
equivalent  direct  radiation  by  dividing  it  by  240  foi  steam,  and  150  for 
water.  This  gives  what  is  called  the  A merican  Gas  Association  rating,  and 
is  the  manner  in  which  all  appliances  approved  by  the  American  Gas 
Association  Laboratory  are  rated.  To  use  these  ratings  it  is  only  necessary 
to  increase  the  calculated  heat  loss  or  the  equivalent  direct  radiation  load 
by  an  appropriate  amount  for  starting  and  piping,  and  to  select  the  boiler 
or  furnace  with  the  proper  rating. 

The  rating  given  by  the  American  Gas  Association  Laboratory  is  not 
only  a  conservative  rating  when  considered  from  the  standpoint  of 
capacity  and  efficiency,  but  is  also  a  safe  rating  when  considered  from  the 
standpoint  of  physical  safety  to  the  owner  or  caretaker.  The  rating  that 
is  placed  upon  an  appliance  is  limited  by  the  amount  of  gas  that  can  be 
burned  without  the  production  of  harmful  amounts  of  carbon  monoxide. 
This  same  limitation  applies  to  all  classes  of  gas-consuming  heating 
appliances  that  are  tested  and  approved  by  the  Laboratory.  Gas  boilers 
are  available  with  ratings  up  to  14,000  sq  ft  of  steam,  while  furnaces  with 
ratings  up  to  about  500,000  Btu  per  hour  are  available.  (See  Chapter  20.) 

REFERENCES 

Stoker  Information,  Bulletin  No.  5,  Committee  of  Ten,  307  N.  Michigan  Ave., 
Chicago,  III. 

Domestic  Burners  for  Pennsylvania  Anthracite,  Commercial  Standard  CS48-34 
U.  S.  Department  of  Commerce. 

Performance  Expectancy  of  Domestic  Underfeed  Stokers  for  Anthracite,  by  Allen  J. 
Johnson  (Transactions,  A.I.M.E.,  Coal  Division,  Vol.  119,  1936). 

The  Relation  of  the  Size  of  Bituminous  Coals  to  Their  Performance  on  Small  Under- 
feed Stokers — The  Relation  of  the  Size  in  the  Hopper  to  That  Burned  in  the  Retort, 
by  R.  A.  Sherman  and  E.  R.  Kaiser,  Technical  Report  No.  1,  Bituminous  Coal  Research, 
Inc.,  (December,  1935)  Pt.  I. 

The  Relation  of  the  Size  of  Bituminous  Coals  to  Their  Performance  on  Small  Under- 
feed Stokers — Burning  Tests  on  Four  Typical  Coals,  by  R.  A.  Sherman,  E.  R.  Kaiser  and 
H.  R.  Limbacher,  Technical  Report  No.  1,  Bituminous  Coal  Research,  Inc.  (July,  1937) 
Pt.  II. 

Stoker  Coals,  Anonymous,  Bulletin  of  Chesapeake  and  Ohio  Railway  Co.,  1935. 

Study  of  Performance  Characteristics  of  Oil  Burners  and  Low  Pressure  Heating 
Boilers,  by  L.  E.  Seeley  and  E.  J.  Tavanlar  (A.S.H.V.E.  TRANSACTIONS,  Vol.  37,  1931, 
p.  517). 

A  Study  of  Intermittent  Operation  of  Oil  Burners,  by  L.  E.  Seeley  and  J.  H.  Powers 
(A.S.H.V.E.  TRANSACTIONS,  Vol.  38,  1932,  p.  317). 

226 


CHAPTER  11.   AUTOMATIC  FUEL  BURNING  EQUIPMENT 


Air  Supply  and  Its  Effect  on  Performance  of  Oil  Burners  and  Heating  Boilers,  by 
L.  E.  Seeley,"  J.  H.  Powers  and  E.  J.  Tavanlar  (A.S.H.V.E.  TRANSACTIONS,  Vol.  39,  1933, 
p.  7,5). 

Study  of  Fuel  Burning  Rates  and  Power  Requirements  of  Oil  Burners  in  Relation  to 
Excess  Air,  by  L.  E.  Seeley  and  E.  J.  Tavanlar  (A.S.H.V.E.  TRANSACTIONS,  Vol.  40, 

1934,  p.  319). 

Oil  Burning  in  Residences,  by  D.  W.  Nelson  (A.S.H.V.E.  TRANSACTIONS,  Vol.  41, 

1935,  p.  355). 

Domestic  Oil  Burners,  by  A.  H.  Senner  (Mechanical  Engineering,  November,  1936). 

A  Study  of  Oil-Fired  Heating  Boilers,  by  R.  C.  Cross  and  \V.  R.  Lyman  (Heating  and 
Ventilating,  October,  1931). 

Value  of  Oil  Burner  Installation  Surveys,  by  R.  C.  Cross  and  W.  R.  Lyman  (Heating 
and  Ventilating,  January,  1931). 

House  Heating,  Industrial  Gas  Series,  American  Gas  Association. 

Approval  Requirements  of  Central  House  Heating  Gas  Appliances,  American  Gas 
Association. 

A  Method  for  Determining  Fuel  Burning  Rates  in  Heating  Boilers  Fired  by  Auto- 
matic Devices,  by  R.  C.  Cross  (Heating  and  Ventilating,  January,  1932). 

Heat  Losses  and  Efficiencies  of  Fuels  in  Residential  Heating,  by  R.  A.  Sherman  and 
R.  C.  Cross  (A.S.H.V.E.  JOURNAL  SECTION,  Heating,  Piping  and  Air  Conditioning, 
January,  1937,  p.  53). 

Efficiencies  and  Costs  of  Various  Fuels  in  Domestic  Heating,  by  R.  A.  Sherman  and 
R.  C.  Cross,  Technical  Report  No.  3,  Bituminous  Coal  Research,  Inc.,  (December,  1936). 

Automatic  Heating  Equipment,  American  Architect  Reference  Data,  No.  7,  September, 
1933. 


PROBLEMS  IN  PRACTICE 

1  •  List  some  factors  which  might  account  for  higher  efficiencies  with  stoker 
firing  than  with  hand  firing. 

a.  The  uniform  rate  of  coal  feed,  b.  Better  distribution  in  the  fuel  bed,  and  c.  Positive 
control  of  the  air  supplied  for  combustion. 

2  •  Classify  stokers  as  to  construction  and  operation. 

a.  Overfeed  flat  grate,  b.  Overfeed  inclined  grate,  c.  Underfeed  side  cleaning  type,  and 
d.  Underfeed  rear  cleaning  type. 

3  •  What  classification  may  he  made  of  stokers  as  to  their  use? 

Class  1.  For  residences  (Capacity  up  to  60  Ib  of  coal  per  hour). 

Class  2.  For  apartment  houses  and  small  commercial  heating  plants  (Capacity  60  to  IOC 
Ib  of  coal  per  hour). 

Class  3.  For  medium  sized  commercial  heating  plants  (Capacity  100  to  300  Ib  of  coa 
per  hour). 

Class  4.  For  large  commercial  plants  and  small  high  pressure  steam  plants  (Capacity 
300  to  1200  Ib  of  coal  per  hour). 

4  •  What  main  parts  are  found  in  an  underfeed  residential  stoker? 

A  hopper  is  supplied  to  hold  coal  which  is  fed  by  a  screw  or  plunger  into  a  retort  provide 
with  air  openings  called  tuyeres.  A  blower  supplies  air  under  pressure  for  combustion,  an 
a  gear  case  provides  for  changes  in  coal  feeding  rates. 

5  •  What  is  a  dead-plate? 

A  dead-plate  is  a  flat  surface  without  air  supply  openings  upon  which  the  fuel  rests  whi 
combustion  of  the  fixed  carbon  is  completed.  Generally  the  ash  is  removed  from  tl 
dead-plate. 

227 


HEATING   VENTUJLTING  AIR  CONDITIONING  GUIDE  1938 

6  •  What  features  of  furnace  design  are  essential  for  the  proper  burning  of 
the  volatile  coal  gases  above  the  fuel  bed? 

Adequate  provisions  should  be  made  so  that  the  furnace  volume  is  sufficiently  liberal 
and  that  the  grates  are  a  sufficient  distance  from  the  heating  surfaces  to  permit  the 
proper  combustion  of  gases- 

7  •  What  methods  of  oil  atomization  are  used? 

a.  Throwing  the  oil  from  a  rotating  cup  or  disc,  b.  Forcing  the  oil  under  high  pressure 
through  a  nozzle,  c.  Propelling  the  oil  with  a  high  velocity  jet  of  air  or  steam,  and  d. 
Forcing  an  oil  and  air  mixture  through  a  nozzle. 

8  •  What  is  the  purpose  of  atomization? 

Atomization  is  used  to  increase  the  surface  area  of  the  oil  in  order  to  facilitate  putting  it 
into  a  vaporous  state  so  it  may  burn. 

9  •  Is  the  furnace  of  much  importance  in  oil  burning? 

In  most  cases  it  is  very  important.  It  is  the  function  of  the  oil  burner  to  supply  the  air 
and  fuel  in  correct  proportions;  the  furnace  must  provide  heated  space  for  proper  mixing 
and  combustion. 

10  •  Which  flame  is  considered  better,  the  luminous  or  the  non-luminous? 

Laboratory  tests  show  that  they  are  equally  efficient  in  the  usual  installation. 

11  •  How  should  oil  burner  adjustments  be  made? 

Adjustments  should  be  made  by  an  experienced  man  who  uses  a  gas  analysis  apparatus 
to  determine  the  COz  content. 

12  •  What  CO2  content  should  be  attained  in  oil  burning? 

Ten  per  cent  COt  is  considered  good  practice,  for  it  indicates  the  supplying  of  50  per  cent 
excess  air. 

13  •  What  maximum  heat  release  is  considered  good  practice  in  oil  burning? 

A  heat  release  of  38,000  Btu  per  cubic  foot  per  hour  is  considered  to  be  the  maximum  for 
average  large  installations.  This  figure  has  been  greatly  exceeded  in  some  cases.  _The 
design  of  the  combustion  chamber,  as  to  impingement  of  flame  and  as  to  proper  mixing 
at  high  temperatures,  has  much  to  do  with  the  attainable  heat  release. 

14  •  Name  five  types  of  gas-fired  space  heaters. 

a.  Parlor  furnaces  or  circulators. 

b.  Radiant  heaters. 

c.  Gas-fired  steam  or  hot  water  radiators. 

d.  Warm  air  radiators. 
«.  Garage  heaters. 

15  •  How  are  gas  heating  units  rated? 

Gas-fired  units  are  rated  on  the  basis  of  output  in  Btu  per  hour. 

16  •  What  safety  consideration  is  noted  in  establishing  the  ratings  of  gas-fired 
units? 

The  rating  is  limited  by  the  amount  of  gas  that  can  be  burned  without  the  liberation  of 
harmful  amounts  of  carbon  monoxide. 


228 


Chapter  12 

HEAT  AND  FUEL  UTILIZATION 

Total  Heat  Loss  Requirements,  Utilization  Factors,  Degree- 

Day  Methods,   Base  Temperature  Determinations,   Steam 

Consumption  of  Buildings,  Fuel  Consumption,  Maximum 

Demands,  Load  Factors 

/HTVHE  hourly  heat  loss  (If)  is  equal  to  the  sum  of  the  transmission 

1  losses  (fit)  and  the  infiltration  losses  (Hi)  of  the  rooms  or  spaces  to 

be  heated.    The  total  equivalent  heating  surface  required  is  equal  to 


In  estimating  the  fuel  consumption  of  a  building  of  more  than  one 
room  divided  by  walls  or  partitions,  it  is  not  correct  to  use  the  calculated 
heat  loss  of  the  building  without  making  the  proper  allowances  for  the 
fact  that  the  heating  load  at  any  time  does  not  involve  the  sum  of  the 
infiltration  losses  of  all  the  heated  spaces  of  the  building  but  only  part  of 
the  infiltration  losses.  This  is  explained  in  Chapter  6. 

It  is  sufficiently  accurate  in  most  cases  to  consider  only  half  of  the  total 
infiltration  losses  of  a  building  having  interior  walls  and  partitions.  The 
value  of  H  in  Equation  1  would,  under  these  conditions,  be  equal  to 

Hi  +  -~.    In  some  cases,  where  the  building  has  no  interior  walls  or 
2> 

partitions,  the  infiltration  losses  are  calculated  by  using  only  half  of  the 
total  crack.  In  this  case  the  entire  infiltration  loss  should  be  considered. 
The  heat  required  to  warm  the  cold  building  and  contents  is  a  factor  to 
be  considered.  Under  certain  conditions  the  cooling  of  the  structure  and 
contents  will,  to  some  extent,  compensate  for  the  heat  required  to  rewarm 
the  building.  For  example,  if  the  building  is  under  thermostatic  control 
and  the  day  and  night  temperatures  are,  70  F  and  50  F  respectively,  there 
will  be  a  period  during  which  no  heat  will  be  added  while  the  building  is 
cooling  to  50  F,  and  the  saving  resulting  therefrom  will  correspond  to  the 
additional  heat  required  to  bring  the  building  and  contents  back  to  the 
daytime  temperature. 

ESTIMATING  FUEL  CONSUMPTION 

There  are  two  methods  in  use  for  estimating  heat  or  fuel  consumption. 
One  method  is  theoretical,  based  on  a  calculated  heat  loss  and  assuming 
absolute  constant  temperatures  for  very  definite  hours  each  day  through- 
out the  entire  heating  season.  It  does  not  take  into  account  factors  which 
are  difficult  to  evaluate  such  as  opening  of  windows,  abnormal  heating  of 
the  building,  sun  effect,  poor  heating  systems,  etc. 

229 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 

The  second  method  is  based  on  steam  consumption  data  which  have 
been  taken  from  a  group  of  buildings  in  operation,  and  the  results  com- 
puted on  a  degree-day  basis.  While  this  method  may  not  be  as  theo- 
retically correct  as  the  first  mentioned  method,  it  is  of  more  value  for 
practical  use.  Calculations  of  heat  consumption  made  by  the  second 
method  will  invariably  be  higher  than  calculations  made  by  the  first 
method. 

Theoretical  Estimation  Method 

To  predict  the  amount  of  fuel  likely  to  be  consumed  in  heating  a 
building  during  a  normal  heating  season,  it  is  necessary  to  know  the  total 
heat  requirements  of  the  building  and  the  utilization  factor  of  the  fuel. 
The  accuracy  of  the  estimate  will  depend  on  the  ability  to  select  these 
values  and  on  the  care  taken  in  making  allowances  for  other  variable 
factors. 

Heat  requirements  are  given  by  the  following  general  formula: 


Steam  requirements  are  determined  by  dividing  the  above  by  1000, 
thus: 


fa  -  to)  1000 
Fuel  requirements  may  be  determined  by  the  following  formula: 


(2) 


where 

t  =s  inside  temperature,  degrees  Fahrenheit. 
id  =  inside  design  temperature,  degrees  Fahrenheit. 

/a  =  average  outside  temperature,  degrees  Fahrenheit  (Table  2,  Chapter  7). 
2o  —  outside  design  temperature,  degrees  Fahrenheit. 

H  =  calculated  heat  loss  of  building  based  on  outside  temperature  (/o),  Btu  per  hour. 
N  =  number  of  heating  hours  per  season;  5088  from  October  1  to  May  I1. 
M  =  heat  loss,  Btu  per  season. 
5  =  steam  required  to  supply  M  Btu  of  heat  loss. 
F  =  quantity  of  fuel  required  per  heating  season. 
C  —  calorific  value  of  one  unit  of  fuel,  the  unit  being  the  same  as  that  on  which 

F  is  based. 
E  =  efficiency  of  utilization  of  the  fuel,  per  cent. 

Example  1.  A  small  factory  building  located  in  Philadelphia  is  to  be  heated  to  60  F 
between  the  hours  of  7  A.M.  and  7  P.M.,  and  to  50  F  during  the  remaining  hours.  The 
calculated  hourly  heat  loss  based  on  a  design  temperature  of  —  6  F  is  500,000  Btu.  If 
coal  having  a  calorific  value  of  12,500  Btu  is  fired  and  the  overall  heating  efficiency  is 
assumed  to  be  60  per_cent,  how  many  pounds  of  steam  would  be  required  for  a  normal 
heating  season? 

lThis  is  the  period  for  which  t*  (Table  2,  Chapter  7)  is  calculated.  If  the  heating  season  is  different 
than  this  period,  the  corrected  values  may  be  substituted  for  N  and  t*. 

230 


CHAPTER  12.   HEAT  AND  FUEL  UTILIZATION 


Solution.  Since  there  are  no  partitions  in  the  building,  the  entire  heat  loss  is  con- 
sidered. From  Table  2,  Chapter  7,  the  average  outside  temperature  ('fe)  during  the 
heating  season  is  42.7  F;  N  for  the  period  for  which  fe.  is  taken  (October  1  to  May  1)  is 
5088;  H  =  500,000;  to  «  -6  F;  *  =  50  F  and  60  F;  fo  =  60  F;  E  =  00  per  cent 
average  for  heating  season;  C  -  12,500. 

The  average  daily  temperature  for  the  24  hours  is: 

50  X  12  +  60  _X  12  ^  55 

Substituting  in  Equation  1: 

M  =   500,000  X  (55  -  42.7)  X  5088 
60 -(-6) 

S  =  474,100  Ib  of  steam. 

nor, 

.x-  *  63,200  Ib  of  coal  =  31.5  tons. 


Practical  or  Degree-Day  Method 

The  amount  of  heat  required  by  a  building  depends  upon  the  outdoor 
temperature,  if  other  variables  are  eliminated.  Theoretically  it  is  pro- 
portional to  the  difference  between  the  outdoor  and  indoor  temperatures. 
Some^years  ago  the  American  Gas  Association*  determined  from  experi- 
ment in  the  heating  of  residences  that  the  gas  consumption  varied  directly 
as  the  difference  between  65  F  and  the  outside  temperature.  In  other 
words,  on  a  day  when  the  temperature  was  20  deg  below  65  F,  twice  as 
much  gas  was  consumed  as  on  a  day  when  the  temperature  was  10  deg 
below  65  F.  The  degree  day  is  defined  in  Chapter  45.  Degree-days  for 
various  cities  in  the  United  States  and  Canada  are  given  in  Table  1. 

Establishing  the  Base  Inside  Temperature.  Recently  the  National 
District  Heating  Association  has  studied  the  metered  steam  consumption 
of  163  buildings3  in  22  different  cities  and  has  published  data  substanti- 
ating the  fact  that  the  65  F  base  originally  chosen  by  the  gas  industry  is 
approximately  correct. 

The  steam  consumption  of  each  building  by  months  was  divided  by  the 
number  of  days  in  each  month,  thus  giving  the  average  daily  steam  con- 
sumption by  months.  The  average  steam  consumption  was  then  plotted 
against  the  average  monthly  temperature,  as  shown  in  Fig,  1,  and  the 
temperature  at  which  a  line  drawn  through  the  points  crossed  the  base 
line  indicated  the  temperature  corresponding  to  zero  steam  consumption, 
or  the  base  temperature.  The  composite  results  from  163  buildings 
calculated  in  this  manner  are  shown  in  Table  2. 

The  resultant  average  of  66.0  F  is  close  to  the  A.G.A.  figure  of  65  F. 
It  will  be  noted  that  the  base  temperature  calculated  for  hotels,  apart- 
ments and  residences  is  consistently  higher  than  those  for  such  buildings 
as  garages,  auto  sales  buildings,  and  manufacturing  buildings.  This,  of 
course,  would  be  expected  in  view  of  the  higher  inside  temperatures 
carried  in  the  former  group;  in  fact,  an  even  greater  difference  would  be 


3See  Industrial  Gas  Series,  House  Heating  (third  edition)  published  by  the  American.  Gas  Association. 
'These  buildings  are  all  served  with  steam  from  a  district  heating  company. 

231 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


TABLE  1.    DEGREE-DAYS  FOR  CITIES  IN  THE  UNITED  STATES  AND  CANADA* 


STATE        ,                Cnr 

JAN. 

FEB. 

MAR. 

APR. 

MAY 

SEPT 

OCT. 

Nov 

DEC 

TOTAL 

Ala  
Ariz  
Ark  
Calif  
Col.. 

Birmingham  
Mobile 

.   589 
.  428 
.1153 
459 

577 
311 
969 
325 

260 
152 

i  896 
257 

69 

318 
186 
840 
252 

595 
394 
1128 
465 

"651 
301 
428 
1067 
1017 
1017 

2408 
1471 
7145 
1845 
2665 
2811 
1504 
3264 
6553 
5873 
5895 
4626 
890 
2891 
1490 
4558 
4924 
6315 
5370 
4164 
5297 
6373 
7023 
5034 
5301 
4616 
4180 
1023 
8531 
7012 
4533 
6045 
6464 
6494 
8692 
9480 
7851 
1822 
5202 
4585 
7115 
8699 
6231 
6128 
5891 
6852 
5175 
4934 
6063 
6889 
6821 
5348 
6785 
3234 
2302 
8498 

"577 

Flagstaff  
Tucson  

Hot  Springs 

654 
87 

636b 

292d 

Little  Rock  

719 
i  326 
!  465 
1085 
1079 
1110 

582 
266 
356 
993 
918 
1011 

353 
239 
354 
884 
799 
899 

78 
159 
294 
612 
534 
543 

"96" 
458b 
459b 
267 
223 

502c 
162 
72 
39 

47 

"146 
502 
428 
360 

381 
123 
261 
789 
759 
693 

"™7S 
396 
201 
738 

Los  Angeles._  
San  Francisco  
Colorado  Springs.. 
Denver.-  

Conn....  
D.  C  

New  Haven™  
Washington  

Fla. 
Ga. 

Jacksonville  
Atlanta  „  . 

285 
682 
409 
1098 

207 
558 
316 
848 

56 
388 
167 
651 

"m 

235" 

108"" 

""96 
*434 

267 
639 
397 
1011 

Idaho 

Savannah.  

Boise 

435 

III  

Lewiston  

Chicago 

1262 
1180 
949 
1128 
1392 
1434 
1116 
1221 
974 
939 
332 
1380 
1321 
955 
1150 

1095 
1008 
854 
969 
1173 
1386 
890 
980 
867 
801 
230 
232 
168 
843 
042 

909 
760 
640 
756 
890 
967 
688 
741 
648 
589 
58 
1110 
1017 
700 
908 

549 
365 
276 
384 
429 
489 
342 
339 
342 
264 

"786 
642 
348 
570 

248 
56 

"58" 
118 
164 
46 

30 
"33" 

353 
282 
155 
298 
357 
415 
276 
270 
245 
186 

756 
681 
528 
687 
798 
870 
672 
699 
612 
552 
102 
843 
780 
567 
693 

"777 
960 
062 
963 
252 
605 
597 
909 
041 

1113 
1038 
862 
1017 
1216 
1265 
1004 
1051 
903 
849 
301 
1228 
1153 
875 
1026 

lTl3 
1301 
1491 
1405 
471 
1038 
936 
192 
383 

"174 
974 
234 
893 
930 
073 
147 
104 
955 
140 
694 
527 

Ind  
Iowa  
Kans  —  
Ky  
La  

Springfield.-  
Evansville  
Indianapolis  
Des  Moines._  
Sioux  City._  
Dodge  City  
Topeka  

Lexington  
Louisville.-  
New  Orleans  

25 



Me._  

Md  

Mass..  

Eastport  
Portland  
Baltimore.  
Boston 

843b 
368 
22 
245 

226" 
682b 
22b 
35 

566^ 
120 

543 
443 
223 
363 

"5)0 
567 
620 
481 

"285 
205 
524 
620 

328 
452 
484 
254 
242 
459 
446 
418 
276 
426 
130 
19 

48 

~42~ 

268<i 
298d 
93 

Mich  
Minn  — 

Springfield  
Detroit.  
Marquette.  
Duluth  

1253 
1501 
1727 
1609 
520 
?01 

134 
360 
473 
400 
384 
987 
854 
120 
450 

125 
823 
240 
903 
942 
902 
142 
156 
960 
181 
630 
468 

976 
249 
277 
095 
195 
750 
657 
955 
168 

868 
753 
Oil 
806 
735 
775 
980 
032 
837 
991 
446 
322 

573 
804 
810 
570 

Miss  
Mo  

Minneapolis  
Vicksburg  

Kansas  City  
St.  Louis  
Billings  
Havre.  
Lincoln  
Omaha  
Reno 

321 
276 
534 
630 

414 
534 
669 
519 
402 
543 
549 
675 
486 
587 
183 
108 

15 

76b 
13 

84*" 
56b 
Sib 
20 
81 
Olb 
93 
47 
55 
44 

Mont  
Nebr  

Nev. 

1060 
1316 
1624 

1355 
1041 
1349 
992 
014 
110 
286 
240 
061 
242 
722 
555 

89 
70 

S" 
68 

20" 

72 
75 

87" 

780 
714 
846 
588 
588 
780 
774 
774 
618 
787 
429 
303 

N.  H  

Concord 

N.  J  _ 

Atlantic  City 

N.  M  „ 
N.  Y  

N.  C  

NT.  Dak  

Trenton  
Santa  Fe  
Albany.  
Buffalo  
New  York  
Utica  
Raleigh  
Wilmington  
Bismarck.  

•Heating  and  Ventilating  Degree-Day  Handbook. 
o  Including  June. 


clncluding  July  and  August, 
d Including  August. 


232 


CHAPTER  12.   HEAT  AND  FUEL  UTILIZATION 


TABLE  1.   DEGREE-DAYS  FOR  CITIES  IN  THE  UNITED  STATES  AND  CANADA*  (Continued) 


STATE 

Crrr 

JAN. 

FEB. 

MAE. 

APR. 

MAT 

SlPT. 

OCT. 

Nov. 

DEC. 

TOTAL 

Ohio  

Okla  

Oree. 

Cincinnati  
Cleveland  
Columbus  

Oklahoma  City.  
Portland 

1076 
1180 
1113 
865 
806 

910 
1075 
980 
742 
644 

747 
950 
703 
465 
558 

378 
564 
420 
162 
402 

73 
220 
87 

335~b 

Tf 
165" 

290 
366 
313 
105 
332 

675 
732 
690 
459 
558 

980 
1060 
1017 
815 
728 

5129 
6154 
5323 
3613 
4468 
4629 
4855 
5235 
6014 
1769 
3257 
7683 
2950 
3578 
1578 
2455 
1157 
1202 
6735 
5553 
7620 
4243 
3349 
3725 
4968 
6353 
5016 
4884 
7612 
7823 
7290 
7372 
7462 

v    & 
Pa  
R.  I  

g^  £  

S.  Dak  
Tenn  

Texas  

Utah  

Vt... 
Va  

Wash  
W.  Va  
Wis  

Wyo  

Salem.  

Philadelphia  
Pittsburgh.  
Providence.  
Charleston.  
Spartanburg  
Sioux  Falls  
Memphis  
Nashville  _ 
Austin  

1001 
1054 
1116 
487 
725 

"744 
812 

895 
944 
1069 
372 
688 

"599 
747 

756 
787 
890 
242 
431 

"384 
476 

402 
423 
558 
36 
147 

""96 
180 

68 
78 
251 

"63" 

242 
313 

«54o 

"iTl" 
_ 

136 

588 
669 
693 
207 
429 

"402 
483 

903 
967 
1026 
425 
716 

"663 
744 

"335 
347 
1218 
1020 
1286 
878 
685 
765 
716 
1057 
977 

1328 
1322 
1280 
1222 
1143 

Dallas  
Houston—  
San  Antonio  
Logan  ... 
Salt  Lake  City....!! 
Burlington  
Fredericksburg  
Norfolk  

Io6 
381 
1260 
1110 
1535 
887 
738 
825 
775 
1171 
1026 

1507 
1538 
1535 
1383 
1215 

"277 
274 
1072 
885 
1294 
820 
650 
702 
653 
952 
944 

1321 
1358 
1265 
1328 
1075 

"~65 
74 
893 
722 
1089 
583 
520 
552 
623 
778 
713 

1046 
1125 
1032 
1023 
995 



376" 
234 
276b 

"468 
388 
481 
223 
99 
158 
403 
514 
294 

"493 
505 
462 
449 
605 

Tl4 
126 
819 
723 
861 
549 
411 
483 
570 
819 
648 

"921 
921 
909 
846 
900 

~iiT 

18 
144 

525 
453 
654 
303 
246 
240 
465 
504 
414 

"603 
600 
528 
648 
720 

Richmond  
Seattle  
Spokane.  
Morgantown  
Parkersburg  
Fond  du  Lac.  
Green  Bay.  
LaCrosse  

487b 
366 

276" 
322 
183 
389*> 
569 

276= 
192 

117" 
132 
96 
84 
240 

Milwaukee.  
Cheyenne.  

PROVINCE 

Cm 

JAN. 

FEB. 

MAE. 

APR. 

MAT 

SEPT. 

OCT. 

Nov. 

Die. 

TOTAL 

B.  C. 

Victoria  

5777 

Alb  

Vancouver.  
Kamloops  

Medicine  Hat._ 



















5976 
6724 
8152 

Sask  
Man  

Qu'Appelle.  
Winnipeg- 



















11,261 
11,166 

Ont  

Port  Arthur.  
Toronto  -...  . 



















10,803 

7732 

Que  

N.  B  
N.  S  
P.  E.  I..... 

Montreal  
Quebec  
Fredericton  
Yarmouth  

Charlottetown  

1615 

1409 

1219 

720 

309 

190 

372 

961 

1422 

8417 
8628 
9099 

7694 
8485 

aHeating  and  Ventilating  Degree-Day  Handbook. 
^Including  June, 
elududing  July  and  August. 


233 


HEATING  VENTILATING  AIR  CONDITIONING   GUIDE  1938 


TABLE  2.    BASE  TEMPERATURE  FOR  THE  DEGREE-DAY** 


TTPI  or  BUILDING 

No.  OF  BUILDINGS 
ANALYZED 

TEMPERATURE  F  COR- 
RESPONDS TO  ZERO 
STEAM  CONSUMPTION 

Office  

60 
4 
3 
2 
6 
11 
12 
7 
14 
S 
4 
5 
3 
2 
2 
4 
3 
3 
2 
8 

66.2 
65.8 
66.2 
65.5 
67.4 
64.0 
64.3 
66.5 
68.8 
66.9 
65.5 
64.9 
67.6 
65.8 
64.8 
61.2 
67.7 
67.7 
65.2 
65.4 

Office  and  Bank. 

Bank  

Office  and  Telephone  Exchange  
Office  and  Stores  

Stores.  ._  . 

Department  Stores  

Hotels........  .„  „..._.  „ 

Apartments.  _ 

Residences.  

Clubs  

Lodges  _  

Theatres... 

Churches.  

Garage.  
Auto  Sales  and  Service.  

Newspaper  and  Printing 

Warehouse  and  Loft  

Office  and  Loft.  
Manufacturing  

Average  for  163  Buildings  

66.  OF 

•Report  of  Commercial  Relations  Committee,  19S£  Proceedings,  National  District  Heating  Association. 

TABLE  3.   STEAM  CONSUMPTION  FOR  VARIOUS  CLASSES  OF  BuiLDiNGsa 
(Heating  Season  Only) 


BUILDING  CLASSIFICATION 

No.  OF 
BUILDINGS 

STEAM  CONSUMPTION 
POUNDS  PER  DEGREE-DAT—  65  F  BASIS* 

Per  M  Cu  Ft 
of  Heated 
Space 

Per  M  Sq  Ft 
of  Radiatorc 
Surface 

PerMBto 
perHrof 
HeatLossb 

Apartments  

16 
10 
12 
7 
10 
18 
6 
16 
7 
8 
6 
14 
6 
35 
35 

1.78 
1.46 
1.32 
1.25 
0.96 
0.90 
0.90 
0.89 
0.88 
0.83 
0.58 
0.57 
0.42 
1.09 
0.975 

97.5 

80.6 
64.2 
105.5 
77.0 
80.6 
75.0 
72.3 
45.2 
62.2 
49.4 
60.7 
72.3 
70.0 
65.4 

0.359 
0.371 

Hotels  

Residences  
Printing  

Clubs  and  Lodges.  

Retail  Stores  

Theatres.   .. 

0.268 
0.498 
0.283 

Loft  and  Mfg  _  

Banks 

Auto  Sales  and  Service  

Churches  

67238 

Department  Stores.  

Garages  (Storage)6.  _    

Offices  (Total)  „. 

0.283 
0.256 

Offices  (Heating  only)  

•Includes  steam  for  heating  domestic  water  for  heating  season  only. 

BHeat  loss  calculated  for  maximum  design  condition  (in  most  cases  70  F  inside,  zero  outside). 

cEquivalent  steam  radiator  surface. 

dThe  figures  are  a  numerical— not  a  -weighted — average  for  the  several  buildings  in  each  class. 

"Based  on  zero  consumption  at  55  F. 


234 


CHAPTER  12.   HEAT  AND  FUEL  UTILIZATION 


expected.  For  an  average  figure,  the  A  .G.A .  base  of  65  F  may  therefore  be 
safely  used,  and  if  greater  refinement  is  desired,  the  figure  for  the  type  of 
building  under  consideration  can  be  taken  from  Table  2. 

Table  34  gives  the  steam  consumption  per  degree-day,  expressed  in 
three  different  ways,  for  196  buildings  in  14  different  classifications. 
These  buildings  are  divided  among  21  different  cities  in  the  United  States. 
The  steam  used  for  heating  the  domestic  water  is  included  in  these 
figures,  but  in  the  case  of  office  buildings,  the  steam  for  heating  only  is 
also  shown.  The  data  are  placed  on  a  comparable  basis  by  expressing 
the  steam  consumption  in  terms  of  pounds  per  degree-day  per  thousand 
square  feet  of  equivalent  installed  radiator  surface,  per  thousand  cubic 
feet  of  heated  space,  and  per  thousand  Btu  of  calculated  heat  loss. 


3  PER  DAY 

<? 

V 

\ 

3  — 

X 

^ 

^ 

\ 

STEAM  CONSl 

\ 

\ 

\ 

AVERAGE  ! 

\ 

^ 

\ 

AVERAGE  TEMPERATURE  FOR  MONTH  DEG  F 

FIG.  1.    METHOD  OF  DETERMINING  BASE  TEMPERATURE  FOR 
DEGREE-DAY  CALCULATIONS6 

The  choice  of  these  units  of  comparison  require  some  explanation. 
The  use  of  heated  space  in  preference  to  the  gross  cubage  used  by  architects 
is  obviously  more  accurate  for  this  purpose.  The  architect's  cubage 
includes  the  outer  walls  and  certain  percentages  of  attic  and  basement 
space  which  are  usually  unheated.  The  net  heated  space  is  usually  about 
80  per  cent  of  the  gross  cubage  and  can  be  calculated  from  the  latter  if  it 
cannot  be  measured.  The  cubical  content  is  somewhat  inaccurate  as  a 
basis  of  comparison  due  to  differences  in  types  of  construction,  exposure, 
and  ratio  of  exposed  area  to  cubical  contents. 

The  use  of  radiator  surface  as  the  basis  of  comparison  has  two  ob- 
jections. One  is  that  the  amount  of  radiator  surface  in  a  building  is  often 
either  excessive  or  deficient,  and  figures  for  steam  consumption  based  on 
it  are  therefore  likely  to  be  in  error.  Another  reason  is  that  it  is  difficult 
to  convert  fan  coil  surface  into  equivalent  direct  radiator  surface  with 
accuracy.  On  the  whole,  the  use  of  radiator  surface  as  the  basis  of  com- 
parison is  the  least  satisfactory  of  the  three  methods. 


*The  Heat  Requirements  of  Buildings,  by  J.  H.  Walker  and  G.  H.  Tuttle  (A.S.H.V.E.  TRANSACTIONS, 
Vol.  41,  1935,  p.  171). 

•Report  of  Commercial  Relations  Committee,  198&  Proceedings,  National  District  Seating  Association. 

235 


HEATING  VENTILATING  Am  CONDITIONING   GUIDE  1938 

It  should  be  noted  that  the  figures  in  Table  3  are  for  the  heating  season 
only  and  include  steam  for  heating  domestic  water. 

Example  1  solved  by  the  degree-day  method  and  using  values  taken 
from  Table  3  would  show  a  higher  steam  consumption. 

Example  8.  Factor  for  steam  consumption  for  a  manufacturing  building  per  M  Btu 
per  hour  heat  loss  per  degree-day  -  0.283;  total  number  of  degree-days  per  year  (Table  1) 
-  4855;  heat  loss  =  500,000  Btu  per  hour. 

Solution.  0.283  X  4855  X  500  -  686,982  Ib  of  steam  per  year.  This  calculation 
results  in  an  estimate  45  per  cent  higher  than  the  previous  calculation  and  one  which 
would  be  more  nearly  correct  for  actual  practice. 


TOO 


600 


500 


J400 


5300 


200 


100 


120 


100 


80 


O 


20 


I  234567B9 

STEAM  CONSUMPTION  -  MILLION  LB 

FIG.  2.    CURVE  FOR  ESTIMATING  FUEL  CONSUMPTION  FOR  VARIOUS 
KNOWN  STEAM  CONSUMPTION* 

•This  curve  is  based  on  heating  efficiencies  of  60  to  70  per  cent  for  coal  and  oil,  respectively,  a  calorific 
value  of  coal  of  13,000  Btu  per  pound,  a  calorific  value  of  oil  of  140,000  Btu  per  gallon. 

In  case  the  heat  loss  figure  is  not  known  this  method  of  estimating  heat 
or  steam  consumption  can  also  be  applied  if  the  net  heated  space  figure 
is  available. 


CALCULATION  OF  FUEL  CONSUMPTION 

After  the  heat  and  steam  consumption  of  the  building  have  been  calcu- 
lated, ^  the  corresponding  fuel  requirements  may  also  be  estimated  by 
assuming  the  correct  boiler  and  furnace  efficiencies.  If  the  building  is  to 
be  supplied  with  steam  from  a  district  heating  company,  the  steam  con- 
sumptions as  calculated  by  the  two  Methods  are  generally  assumed  to  be 
correct.  However,  if  the  steam  is  to  be  supplied  from  an  individual  boiler 

236 


CHAPTER  12.    HEAT  AND  FUEL  UTILIZATION 


unit,  the  consumption  should  be  assumed  as  from  10  to  20  per  cent  greater. 
One  reason  for  this  difference  in  steam  consumption  is  that  district  steam 
is  a  metered^  service,  and  building  managers  are  therefore  more  conscious 
of  their  heating  costs,  which  generally  results  in  better  maintained  heating 
systems.  Also,  the  district  steam  service  is  usually  installed  with  ther- 
mostatic  control  which  reduces  overheating  to  a  minimum. 

Fig.  2  shows  the  amount  of  coal  or  oil  that  may  be  estimated  when  the 
steam  consumption  is  known.    Assuming  the  steam  consumption  that 


1.4 


\ 


1.2 


1-Cu  ft  of  gas  per  sq  ft  installed 

hot  water  radiation 
2-Cu  ft  of  gas  per  sq  ft  installed 

steam  radiation 
3-  Cu  ft  of  gas  per  100  cu  ft  bldg 

contents  hot  air  system 
4- Cu  ft  of  gas  per  1,000  Btu  hourly 
loss  from  bldg.  hot  air  system 


200 


500     600     700 
Btu  VALUE  OF  GAS 


800 


900    1,000    1,100 


FIG.  3.    CHART  GIVING  GAS  REQUIREMENTS  PER  DEGREE-DAY  FOR  VARIOUS  CALORIFIC 
VALUES  OF  GAS  AND  FOR  DIFFERENT  HEATING  SYSTEMS* 

aTbis  chart  is  based  on  an  inside  temperature  of  70  F  and  an  outside  temperature  of  zero.  If  the  radia- 
tion is  installed  on  the  basis  of  any  other  temperature  difference,  multiply  the  result  obtained  from  this 
chart  by  70,  and  divide  by  the  actual  temperature  difference.  From  Industrial  Gas  Series  House  Heating, 
(third  edition)  published  by  the  A  merican  Gas  Association. 

was  calculated  in  Example  2,  686,982  Ib,  the  corresponding  coal  con- 
sumption, from  the  curve,  is  44  tons  and  the  oil  consumption  6000  gal. 

Fig.  3  indicates  the  average  gas  consumption  per  degree-day  for 
various  heat  contents.  While  the  fuel  consumption  in  individual  cases 
may  vary  somewhat  from  the  curve  values,  these  average  values  are 
sufficiently  accurate  for  estimating  purposes  and  give  satisfactory  results. 

The  value  generally  used  in  the  manufactured  gas  industry  for  resi- 
dences is  0.21  cu  ft  per  degree-day  per  square  foot  of  equivalent  steam 
radiation  (240  Btu)  based  on  the  theoretical  requirements.  A  correction 
for  warmer  climates  is  necessary  and  it  is  customary  to  gradually  increase 
the  relative  fuel  consumption  below  3000  degree-days  to  about  20  per  cent 
more  at  1000  degree-days. 

237 


§g 
*l 
-     Si 


HEATING  VENTILATING  AIR  CONDITIONING  GUIDE  1938 


§    CALORIFIC  VALUE  OF  FUEL 
J    BTU  PERLS  -AS  FIRED 


,0-1  K>- 


I       I 


100    '  20O  300 

GROSS  OUTPUT -THOUSAND  BT.U  PER  HOUR 


46  8  10  12  14 

GROSS  OUTPUT-  HUNDRED  FEET  STEAM  RADIATION 


5  10  15  20  25 

GROSS  OUTPUT  -  HUNDRED  FEET  WATER  RADIATION 


FIG.  4.    COAL  FUEL  BURNING  RATE  CHART. 


I2 

SB* 

H* 
*!' 


100  200  300 

GROSS  OUTPUT-THOUSAND  BTU  PER  HOUR 


400 


500 


—i 1 1 1 1 1 1 1 1 1 1 1 

4  6  8  10  12  14 

GROSS  OUTPUT-  HUNDRED  FEET  STEA'M  RADIATION 


i        i        i 1 — 

18  20 


0  5  10  15  -20  25  30 

GROSS  OUTPUT-  HUNDRED  FEET  WATER  RADIATION 
FIG.  5.    OIL  FUEL  BURNING  RATE  CHARTS 

nil  !lbj?o2art  S-kf8^  upon  No: 3  9a  Caving  a  heat  content  of  143,400  Btu  per  gallon.    If  other  grades  of 
2l^2n^iI?S?9l|fe    oe  ^fe ?%fined  from  this  chart  by  the  following  factors:     No.  1  oil  (139,000 ^Btu 

SdfffiSawSi »  4£i?D^n?  25  S  ffi^WJSSi  5?,;  lilflttKPnSS11  per  »**>  a"2» No- 


238 


CHAPTER  12.   HEAT  AND  FUEL  UTILIZATION 


For  hot  water  or  warm  air  heat  the  fuel  consumption  is  about  0.19  cu  ft 
per  degree-day  per  square  foot  of  equivalent  steam  radiation,  that  is,  per 
240  Btu  per  hour.  The  actual  requirements  likewise  relatively  increase 
with  hot  water  or  warm  air  systems  as  the  number  of  degree-days  decreases 
below  3000.  For  larger  installations,  that  is  1000  sq  ft  of  theoretical 
radiation  and  above,  there  is  an  increase  in  efficiency,  and  a  consequent 
decrease  in  the  fuel  consumption  per  degree-day  per  square  foot  of 
heating  surface. 

The  approximate  quantities  of  steam  required  in  New  York  City  per 
square  foot  of  heating  surface  for  various  classes  of  buildings  are  given  in 
Chapter  42. 

The  preceding  discussion  on  fuel  consumption  has  dealt  with  the 
heating  requirements  of  the  building  irrespective  of  any  air  that  may  be 


GROSS  CALORIFIC  VALUE 
O       O    BT.U   PER  CUBIC  FOOT 

CO        O 


800-  500- 


300- 


200- 


200- 


100- 


300 


100 


.     L 


100  200  300 

GROSS  OUTPUT -THOUSAND  &T.UL  PER  HOUR 


500 


4  6  8  10  12  14 

GROSS  OUTPUT-  HUNDRED  FEET  STEAM  RADIATION 


05  IO  15  20  25  30 

GROSS  OUTPUT  -  HUNDRED  FEET    WATER  RADIATION 

FIG.  6.    GAS  FUEL  BURNING  RATE  CHART. 

introduced  for  ventilation  purposes  other  than  the  normal  infiltration  of 
outside  air.  The  heat  required  for  warming  air  brought  into  the  building 
for  ventilation  may  be  estimated  from  data  given  in  Chapters  3  and  21. 

Rate  of  Fuel  Burning 

If  the  estimated  maximum  load  or  gross  output  is  determined  as  out- 
lined in  Chapter  13,  the  fuel  burning  rates  for  coal,  oil,  or  gas  may  be 
determined  from  the  charts  illustrated  in  Figs.  4,  5  and  6.  For  a  given 
efficiency,  the  rate  of  fuel  burning  is  directly  proportional  to  the  gross 
output,  and  therefore,  these  charts  can  be  extended  by  moving  the 
decimal  point  the  same  number  of  digits  in  both  vertical  and  horizontal 
scale.  All  charts  are  based  upon  values  of  one  square  foot  steam  radiation 
equivalent  to  240  Btu  per  hour  and  one  square  foot  hot  water  radiation 
equivalent  to  150  Btu  per  hour.  In  using  these  charts,  consideration 

239 


HEATING  VENTILATING   AIR  CONDITIONING   GUIDE  1938 


must  be  given  to  the  overall  efficiency  of  the  boiler  or  firing  device.  This 
factor  is  largely  dependent  upon  good  judgment  and  is  a  measure  of  the 
degree  of  efficiency  to  be  expected  from  a  particular  installation. 

The  correct  fuel  burning  rate  can  be  determined  directly  from  the 
several  charts  for  oil  or  gas  burning  installations,  as  these  customarily 
operate  on  a  strictly  intermittent  basis.  These  fuel  burning  devices 
usually  introduce  the  fuel  at  a  single  fixed  rate  during  the  on  periods  and 
this  rate  should  be  sufficient  to  carry  the  gross  or  maximum  design  load. 
In  the  case  of  coal  stokers,  which  are  usually  capable  of  variable  rates  of 
firing,  it  is  desirable  to  operate  at  as  low  a  rate  as  weather  conditions  will 
permit,  but  the  maximum  firing  rate  of  the  stoker  should  be  sufficient 
to  carry  the  gross  load.  This  rate  may  be  determined  by  the  same  method 
as  used  for  oil  or  gas. 

In  the  case  of  warm  air  heating  installations  the  heat  loss  of  the  building 
expressed  in  Btu  per  hour  can  be  determined  by  use  of  the  Standard 
Codes6  of  the  National  Warm  Air  Heating  and  Air  Conditioning  Asso- 
ciation. If  the  design  heat  loss  of  the  building  is  divided  by  the  proper 
factor,  the  required  gross  output  may  be  obtained  from  the  proper  charts 
shown  in  Figs.  4,  5  and  6. 

Example  8.^  The  estimated  net  load  (including  domestic  hot  water  supply)  as  calcu- 
lated for  a  residence  is  1500  sq  ft  of  hot  water  radiation.  Determine  the  firing  rates  for 
various  fuels  assuming  an  overall  efficiency  of  70  per  cent ;  using  coal  with  a  calorific  value 
of  12,500  Btu  per  pound;  No.  3  fuel  oil  and  natural  gas  having  a  gross  heating  value  of 
1000  Btu  per  cubic  foot. 

Solution.  Referring  to  Fig.  3,  Chapter  13,  a  piping  and  pick-up  factor  for  a  net  load  of 
1500  sq  ft  is  found  to  be  43  per  cent  or  the  gross  output  is  equivalent  to  1500  X  1.43  = 
2145  sq  ft  hot  water  radiation. 

Using  the  chart  in  Figs.  4,  5  and  6  project  vertically  from  the  gross  output  value  on 
the  proper  horizontal  scale  to  the  intersection  of  the  70  per  cent  efficiency  line.  From  the 
intersection  of  this  line  proceed  horizontally  to  the  proper  vertical  scale  where  a  direct 
value  of  the  required  fuel  burning  rate  is  given.  These  values  are  rates  of  burning  while 
firing  device  is  in  operation  and  are  not  indicative  of  hourly  fuel  consumption. 

By  use  of  the  respective  charts  the  firing  rates  for  the  various  fuels  will  be  found  to  be: 
coal  36.8  Ib  per  hour,  oil  3.2  gal  per  hour,  and  gas  460  cu  ft  per  hour. 

TABLE  4.    BUILDING  LOAD  FACTORS  AND  DEMANDS  OF  SOME  DETROIT  BUILDINGS'* 


BUILDING  CLASSIFICATION 

LOAD  FACTOR 

LB  or  DEMAND  PER  HR 
PER  SQ  FT  OF  EQUIVALENT 
INSTALLED  RADIATOR  SURFACE 

Clubs  and  Lodges  

0  318 

0  184 

Hotels  

0  316 

0  907 

Printing  

0  287 

0  217 

Offices  

0  263 

0  209 

Apartments  

0  255 

0  2^5 

Retail  Stores  

0  238 

0  182 

Auto  Sales  and  Service.—  

0.223 

0  248 

Banks  

0  203 

0  158 

Churches.  

0  158 

0  152 

Department  Stores  

0.138 

0  145 

Theatres  

0  126 

0151 

>Loc.  Cit.  Note  5. 


8  P%  Installation  of  Gravity  Warm  Air  Heating  Systems  in  Residences 

edition)  and  the.  Technical  Code  for  the  Design  and  Installation  of  Mechanical  Warm  Air  Heating 
systems,  may  be  obtained  from  the  National  Warm  Air  Heating  and  Air  Conditioning  Association,  50  W. 
Broad  St.,  Columbus,  Ohio. 

240 


CHAPTER  12.    HEAT  AND  FUEL  UTILIZATION 


MAXIMUM  DEMANDS  AND  LOAD  FACTORS 

In  one  form  of  district  heating  rates,  a  portion  of  the  charge  is  based 
upon  the  maximum  demand  of  the  building.  The  maximum  demand  may 
be  measured  in  several  different  ways.  It  may  be  taken  as  the  instan- 
taneous peak  or  as  the  rate  of  use  during  any  specified  interval.  One 
method  is  to  take  the  average  of  the  three  highest  hours  during  the 
winter.  These  figures  are  available  for  a  number  of  buildings  in  Detroit, 
as  shown  in  Table  4. 

These  maximum  demands  were  measured  by  an  attachment  on  the 
condensation  meter  and  therefore  represent  the  amounts  of  condensation 
passed  through  the  meter  in  the  highest  hours,  rather  than  the  true  rate 
at  which  steam  is  supplied.  There  might  be  slight  differences  in  these 
two  quantities  due  to  time  lag  and  to  storage  of  condensate  in  the  system, 
but  wherever  this  has  been  investigated  it  has  been  found  to  be  negligible. 

The  load  factor  of  a  building  is  the  ratio  of  the  average  load  to  the 
maximum  load  and  is  an  index  of  the  utilization  habits.  Thus,  in  Table  4, 
the  theatres,  operating  for  short  hours,  have  a  load  factor  of  0.126  as 
compared  with  the  figure  of  0.318  for  clubs  and  lodges. 


PROBLEMS  IN  PRACTICE 

1  •  What  will  be  the  cost  per  year  of  heating  a  building  with  gas,  assuming  that 
the  calculated  hourly  heat  loss  is  92,000  Btu  based  on  0  F,  which  includes 
26,000  Btu  for  infiltration?  The  design  temperatures  are  0  F  and  72  F.  The 
normal  heating  season  is  210  days,  and  the  average  outside  temperature  during 
the  heating  season  is  36.4  F.  The  heating  efficiency  will  be  75  per  cent.  The 
heating  plant  will  be  thermostatically  controlled,  and  a  temperature  of  55  F 
will  be  maintained  from  11  p.m.  to  7  a.m.  Assume  that  the  price  of  gas  is 
7  cents  per  100,000  Btu  of  fuel  consumption,  and  disregard  the  loss  of  heat 
through  open  windows  and  doors. 

The  average  hourly  temperature  is 

fc  ,  (72  X  16)  +  (55  X  8)  _  ^  p 

The  maximum  hourly  heat  loss  will  be 
H  -  92,000  - 


79,000  (66.3  -  36.4)  X  24  X  210        00.  .  ,,,,,,,.  ,  Dj. 

=  22046  hundred  thousand  Btu' 


100.000  X  0.75  X  (72-0) 
2204.6  X  0.07  =  $154.34  =  cost  per  year  of  heating  the  building. 

2  •  What  factors  should  be  taken  into  consideration  when  determining  the 
efficiency  at  which  a  fuel  will  be  burned? 

Manufacturers'  catalogs  usually  give  equipment  efficiencies  obtained  under  test  con- 
ditions. These  values  do  not  allow  for  poor  attendance,  defects  in  installation,  or  poor 
draft.  Such  efficiencies  do  not  consider  heat  radiated  from  the  outside  of  the  equipment, 
but  in  many  cases  this  heat  is  utilized. 

241 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

3  •  If  20  tons  of  coal  having  a  calorific  value  of  13,000  Btu  per  pound  are  burned 
in  a  warm  air  furnace  and  produce  236,000,000  Btu  at  the  bonnet,  what  is  the 
efficiency  of  the  furnace? 

_  Number  of  Btu  at  bonnet  _  _     ffi  . 
Number  of  tons  X  calorific  value  X  number  of  pounds  in  one  ton    ~~  e    Clency- 

286,000,000  X  100    _  „ 
20  X  13,000  X  2000  "  65  per  cent- 

4  •  Make  a  rough  approximation  of  the  gas  required  to  heat  a  building  located 
in  Chicago,  111.,  assuming  that  the  calculated  heating  surface  requirements 
are  1000  sq  ft  of  hot  water  radiation  based  on  design  temperatures  of  0  F  and 
70  F.    Chicago  has  800-Btu  mixed  gas,  and  6315  degree-days. 

Using  Fig.  3,  the  fuel  consumption  for  a  design  temperature  of  0  F  with  800-Btu  gas  is 
found  to  be  0.08  cu  ft  of  gas  per  degree-day  per  square  foot  of  hot  water  radiation. 

0.08  X  6315  X  1000  =  505,200  cu  ft. 

5  •  A  certain  building  has  a  maximum  heat  loss  of  250,000  Btu  per  hour  in  —  15  F 
weather.    How  many  tons  of  fuel  will  be  required  to  maintain  a  temperature  of 
70  F  during  a  260-day  heating  season  in  which  the  average  temperature  is  39  F? 
The  heating  value  of  the  fuel  is  13,200  Btu  per  pound  and  the  efficiency  of  com- 
bustion is  60  per  cent. 


250,000  (70  -  39)  260  X  24 
(70  +  15)  13,200  X  0.60  X  2000 


tons' 


6  •  Which  item  may  be  determined  more  closely,  the  heating  value  of  a  fuel  or 
the  efficiency  of  its  combustion? 

The^  heating  values  of  oil,  gas,  and  solid  fuels  are  closely  determinable,  whereas  the 
efficiency  of  burning  depends  on  the  particular  equipment  chosen  and  the  skill  used  in 
handling  it. 

7  •  In  an  office  building,  the  thermostats  are  set  to  maintain  70  F  from  7  a.m. 
to  5  p.m.  and  50  F  during  the  rest  of  the  time.    When  the  outside  temperature 
is  30  F,  how  much  saving  might  be  expected  because  the  temperatures  are 
lowered?    Under  the  above  conditions  the  building  becomes  50  F  by  11  p.m.  and 
warms  up  to  70  F  by  8  a.m. 

A  temperature  of  70  F  is  maintained  during  9  hours,  and  one  of  50  F  during  8  hours;  the 
temperature  would  average  about  60  F  during  the  7  hours  required  for  cooling  down  and 
warming  up.  The  average  is  60.4  for  the  24  hours.  (The  average  temperature  calcu- 
lated would  have  been  58.3  F,  had  the  warming  and  cooling  periods  been  neglected.) 


The  saving  is          1  X  100  =          x  100  -  24  per  cent. 

8  •  How  does  the  heat  capacity  of  a  structure  influence  the  saving  made  by 
carrying  lower  temperatures  during  the  night? 

The  heat  storage  capacity  of  the  walls  prevents  rapid  dropingof  temperatures  at  night- 
time and  delays  the  warming  up  process  in  the  morning.  In  an  extreme  case,  the  building 
would  not  reach  the  lowered  temperature  by  the  time  the  higher  temperature  is  called 
for  in  the  morning.  But  under  any  conditions,  the  saving  made  by  lowering  the  tem- 
perature can  be  correctly  estimated  by  using  the  average  temperature  observed  over  the 
24-hour  period  as  a  factor,  as  in  Question  7. 

9  •  What  are  some  of  the  miscellaneous  factors  that  may  cause  actual  fuel 
consumption  to  vary  from  the  theoretical  fuel  requirements  as  calculated  by 
the  use  of  heat  losses,  temperature  difference,  and  fuel  burning  efficiency? 

The  opening  of  windows;  abnormally  high  or  low  inside  temperatures;  other  sources  of 
heat,  such  as  machinery  or  lights;  sun  effect;  high  occupancy;  and  unusual  winds. 

242 


Chapter  13 

HEATING  BOILERS 

Cast-iron  Boilers,  Steel  Boilers,  Special  Heating  Boilers, 
Gas-Fired  Boilers,  Hot  Water  Supply  Boilers,  Furnace  Design, 
Heating  Surface,  Testing  and  Rating  Codes,  Output  Effic- 
iency, Selection  of  Boilers,  Connections  and  Fittings,  Erection, 
Operation  and  Maintenance,  Boiler  Insulation 

STEAM  and  hot  water  boilers  for  low  pressure  heating  work  are  built  in 
a  wide  variety  of  types,  many  of  which  are  illustrated  in  the  Catalog 
Data  Section,  and  are  classified  as  (1)  cast-iron  sectional,  (2)  steel  fire 
tube,  (3)  steel  water  tube,  and  (4)  special. 

CAST-IRON  BOILERS 

Cast-iron  boilers  may  be  of  round  pattern  with  circular  grate  and  hori- 
zontal pancake  sections  joined  by  push  nipples  and  tie  rods,  or  of  rec- 
tangular pattern  with  vertical  sections.  The  latter  type  may  be  either  of 
outside  header  construction  where  each  section  is  independent  of  the  other 
and  the  water  and  steam  connections  are  made  externally  through  these 
headers,  or  assembled  with  push  nipples  and  tie  rods,  in  which  case  the 
water  and  steam  connections  are  internal. 

Cast-iron  boilers  usually  are  shipped  knocked  down  to  facilitate  hand- 
ling at  the  place  of  installation  where  assembly  is  made.  One  of  the  chief 
advantages  of  cast-iron  boilers  is  that  the  separate  sections  can  be  taken 
into  or  out  of  basements  and  other  places  more  or  less  inaccessible  after 
the  building  is  constructed.  This  feature  is  of  importance  in  making 
repairs  to  or  replacing  a  damaged  or  worn-out  boiler  and  should  be  given 
consideration  in  the  original  selection.  Sufficient  space  should  be  pro- 
vided in  the  boiler  room  for  assembling  the  boiler  and  for  disassembling  it 
conveniently  if  repairs  are  needed.  With  the  outside  header  type  of  boiler 
a  damaged  section  in  the  middle  of  the  boiler  can  be  removed  without 
disturbing  the  other  sections  so  side  clearance  should  be  provided. 

Capacities  of  cast-iron  boilers  range  from  that  required  for  small 
residences  up  to  about  18,000  sq  ft  of  steam  radiation.  For  larger  loads, 
cast-iron  boilers  must  be  installed  in  multiple,  or  a  steel  boiler  must  be 
used.  In  most  cases  cast-iron  boilers  are  limited  to  working  pressures  of 
15  Ib  for  steam  and  30  Ib  for  water.  Special  types  are  built  for  hot  water 
supply  which  will  withstand  higher  local  water  pressures. 

STEEL  BOILERS 

Two  general  classifications  may  be  applied  to  steel  boilers:  first,  with 
regard  to  the  relative  position  of  water  and  hot  gases,  distinguished  as  fire 
tube  or  water  tube;  second,  with  regard  to  arrangement  of  furnace  and 

243 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


flues,  as  (1)  horizontal  return  tubular  (HRT)  boilers,  (2)  portable  (self- 
contained)  firebox  boilers  with  either  water  or  fire  tubes,  and  (3)  water 
tube  boilers  of  the  power  type. 

Fire  tube  boilers  are  constructed  so  that  the  water  available  to  produce 
steam  is  contained  in  comparatively  large  bodies  distributed  outside  of  the 
boiler  tubes,  the  hot  gases  passing  within  the  tubes.  In  water  tube  boilers, 
the  water  is  circulated  within  the  boiler  tubes,  heat  being  applied  ex- 
ternally to  them. 

The  HRT  boiler  is  the  oldest  type  and  consists  of  a  horizontal  cylin- 
drical shell  with  fire  tubes,  enclosed  in  brickwork  to  form  the  furnace  and 

TABLE  1.    PRACTICAL  COMBUSTION  RATES  FOR  SMALL  COAL-FIRED  HEATING  BOILERS 
OPERATING  ON  NATURAL  DRAFT  OF  FROM  y%  IN.  TO  y%  IN.  WATER* 


KIND  OP  COAL 

SQ  FT  GRATE 

LB  or  COAL  PER  SQ  FT 
GRATE  PER  HOUR 

No.  1  Buckwheat  Anthracite 

Up  to  4 
5  to  9 
10  to  14 
15  to  19 
20  to  25 

3 

3H 
4 
&A 
5 

Anthracite  Pea 

Up  to  9 
10  to  19 
20  to  25 

5 
5Ji 
6 

Anthracite  Nut  and  Larger 

Up  to  4 
5  to  9 
10  to  14 
15  to  19 
20  to  25 

8 
9 
10 
11 
13 

Bituminous 

Up  to  4 
5  to  14 
15  and  above 

9.5 
12 
15.5 

aSteel  boilers  usually  have  higher  combustion  rates  for  grate  areas  exceeding  15  sq  ft  than  those  indicated 
in  this  table. 

combustion  chamber.  All  heating  surfaces  and  the  interior  of  the  boiler 
are  accessible  for  both  cleaning  and  inspection.  Horizontal  return  tubular 
boilers,  especially  the  larger  sizes,  should  be  suspended  from  structural 
columns  and  beams  independent  of  the  brick  setting.  Small  HRT  boilers 
sometimes  are  supported  by  brackets  resting  on  the  brick  setting. 

Portable  firebox  boilers  are  the  more  generally  used  type  of  steel  heating 
boilers,  their  outstanding  characteristic  being  the  water- jacketed  firebox 
which  eliminates  virtually  all  brickwork.  They  are  shipped  in  one  piece 
from  the  factory  and  come  to  the  job  ready  for  immediate  hook-up  to 
piping.  They  may  be  of  welded  or  riveted  construction  and  have  either 
water  or  fire  tubes.  Manufacturers'  catalogs  usually  list  heating  surface 
as  well  as  grate  area.  The  elimination  of  brickwork  also  makes  this  type 
the  most  compact  of  steel  boilers  as  well  as  the  lowest  in  first  cost. 

Water  tube  boilers.  For  large  heating  loads  water  tube  boilers  are  quite 
frequently  used.  They  usually  require  more  head  room  than  other  types 
of  boilers  but  require  considerably  less  floor  space  and  make  possible  a 

244 


CHAPTER  13.   HEATING  BOILERS 


much  higher  rate  of  evaporation  per  square  foot  of  heating  surface,  with 
proper  setting,  baffling  and  draft.  Water  tube  boilers  used  for  heating 
purposes  are  either  completely  supported,  insulated  and  encased  in  steel, 
or  else  brick  set,  supported  on  structural  steel  columns  and  have  the  brick 
setting  encased  in  an  insulated  steel  housing  to  prevent  air  infiltration  and 
to  minimize  heat  losses.  For  large  heating  loads  at  a  high  rate  of  evapora- 
tion, such  boilers  should  be  operated  at  pressures  above  15  Ib  per  square 
inch  with  a  pressure-reducing  valve  on  the  connection  to  the  heating  main. 

SPECIAL  HEATING  BOILERS 

A  special  type  of  boiler,  known  as  the  magazine  feed  boiler,  has  been 
developed  for  the  burning  of  small  sizes  of  anthracite  and  coke.  These 
are  built  of  both  cast-iron  and  steel,  and  have  a  large  fuel  carrying 
capacity  which  results  in  longer  firing  periods  than  would  be  the  case  with 
the  standard  types  using  buckwheat  sizes  of  coal.  Special  attention  must  be 
given  to  insure  adequate  draft  and  proper  chimney  sizes  and  connections. 

Oil-burner  boiler  units,  in  which  a  special  boiler  has  been  designed  with 
a  furnace  shaped  to  meet  the  general  requirements  of  oil  burners  or  are 
specially  adapted  to  one  particular  burner  have  been  developed  by  a 
number  of  manufacturers.  These  usually  are  compact  units  with  the 
burner  and  all  controls  enclosed  within  an  insulated  steel  jacket.  Ample 
furnace  volume  is  provided  for  efficient  combustion,  and  the  heating 
surfaces  are  proportioned  for  effective  heat  transfer.  Consequently, 
higher  efficiencies  are  obtainable  than  with  the  ordinary  coal  fired  boiler 
converted  to  oil  firing. 

GAS-FIRED  BOILERS 

Gas  boilers  have  assumed  a  well-defined  individuality.  The  usual  boiler 
is  sectional  in  construction  with  a  number  of  independent  burners  placed 
beneath  the  sections.  In  most  boilers  each  section  has  its  own  burner.  In 
all  cases  the  sections  are  placed  quite  closely  together,  much  closer  than 
would  be  possible  when  burning  a  soot-forming  fuel.  The  effort  of  the 
designer  is  always  to  break  the  hot  gas  up  into  thin  streams,  so  that  all 
particles  of  the  heat-carrying  gases  can  come  as  close  as  possible  to  the 
heat-absorbing  surfaces.  Because  there  is  no  fuel  bed  resistance  and  because 
the  gas  company  supplies  the  motive  power  to  draw  in  the  air  necessary 
for  combustion  (in  the  form  of  the  initial  gas  pressure) ,  draft  losses  through 
gas  boilers  are  low.  See  Chapter  11. 

HOT  WATER  SUPPLY  BOILERS 

Boilers  for  hot  water  supply  are  classified  as  direct,  if  the  water  heated 
passes  through  the  boiler,  and  as  indirect,  if  the  water  heated  does  not 
come  in  contact  with  the  water  or  steam  in  the  boiler. 

Direct  heaters  are  built  to  operate  at  the  pressures  found  in  city  supply 
mains  and  are  tested  at  pressures  from  200  to  300  Ib  per  square  inch. 
The  life  of  direct  heaters  depends  almost  entirely  on  the  scale-making 
properties  of  the  water  supplied.  If  water  temperatures  are  maintained 
below  140  F  the  life  of  the  heater  will  be  much  longer  than  if  higher 
temperatures  are  used,  owing  to  decreased  scale  formation  and  minimized 
corrosion  below  140  F.  Direct  water  heaters  in  some  cases  are  designed 
to  burn  refuse  and  garbage. 

245 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 

Indirect  heaters  generally  consist  of  steam  boilers  in  connection  with 
heat  exchangers  of  the  coil  or  tube  types  which  transmit  the  heat  from  the 
steam  to  the  water.  This  type  of  installation  has  the  following  advantages : 

1.  The  boiler  operates  at  low  pressure. 

2.  The  boiler  is  protected  from  scale  and  corrosion. 

3.  The  scale  is  formed  in  the  heat  exchanger  in  which  the  parts  to  which  the  scale 
is  attached  can  be  cleaned  or  replaced.    The  accumulation  of  scale  does  not  affect 
efficiency  although  it  will  affect  the  capacity  of  the  heat  exchanger. 

4.  Discoloration  of  water  may  be  prevented  if  the  water  supply  comes  in  contact 
with  only  non-ferrous  metal. 

Where  a  steam  heating  system  is  installed,  the  domestic  hot  water 
usually  is  obtained  from  an  indirect  heater  placed  below  the  water  line  of 
the  boiler. 

FURNACE  DESIGN 

Good  efficiency  and  proper  boiler  performance  are  dependent  on  cor- 
rect furnace  design  embodying  sufficient  volume  for  burning  the  par- 
ticular fuel  at  hand,  which  requires  thorough  mixing  of  air  and  gases  at 
a  high  temperature  with  a  velocity  low  enough  to  permit  complete  com- 
bustion of  all  the  volatiles.  On  account  of  the  small  ampunt  of  volatiles 
contained  in  coke,  anthracite,  and  semi-bituminous  coal,  these  fuels  can 
be  burned  efficiently  with  less  furnace  volume  than  is  required  for  bi- 
tuminous coal,  the  combustion  space  being  proportioned  according  to  the 
amount  of  volatiles  present. 

Combustion  should  take  place  before  the  gases  are  cooled  by  the  boiler 
heating  surface,  and  the  volume  of  the  furnace  must  be  sufficient  for  this 
purpose.  The  furnace  temperature  must  be  maintained  sufficiently  high 
to  produce  complete  combustion,  thus  resulting  in  a  higher  CO*  content 
and  the  absence  of  CO.  Hydrocarbon  gases  ignite  at  temperatures 
varying  from  1000  to  1500  F. 

The  question  of  furnace  proportions,  particularly  in  regard  to  mechani- 
cal stoker  installations,  has  been  given  some  consideration  by  various 
manufacturers'  associations.  'Arbitrary  values  have  been  recommended 
for  minimum  dimensions.  A  customary  rule-of -thumb  method  of  figuring 
furnace  volumes  is  to  allow  1  cu  ft  of  space  for  a  maximum  heat  release 
of  50,000  Btu  per  hour.  This  value  is  equivalent  to  allowing  approxi- 
mately 1  cu  ft  for  each  developed  horsepower,  and  it  is  approved  by 
most  smoke  prevention  organizations. 

The  setting  height  will  vary  with  the  type  of  stoker.  In  an  overfeed 
stoker,  for  instance,  all  the  volatiles  must  be  burned  in  the  combustion 
chamber  and,  therefore,  a  greater  distance  should  be  allowed  than  for  an 
underfeed  stoker  where  a  considerable  portion  of  the  gas  is  burned  while 
passing  through  the  incandescent  fuel  bed.  The  design  of  the  boiler  also 
may  affect  the  setting  height,  since  in  certain  types  the  gas  enters  the 
tubes  immediately  after  leaving  the  combustion  chamber,  while  in  others 
it  passes  ^over  a  bridge  wall  and  toward  the  rear,  thus  giving  a  better 
opportunity  for  combustion  by  obtaining  a  longer  travel  before  entering 
the  tubes. 

_  To  secure  ^suitable  furnace  volume,  especially  for  mechanical  stokers  or 
oil  burners,  it  often  is  necessary  either  to  pit  the  stoker  or  oil  burner,  or 

246 


CHAPTER  13.   HEATING  BOILERS 


where  water  line  conditions  and  headroom  permit,  to  raise  the  boiler  on  a 
brick  foundation  setting. 

Smokeless  combustion  of  the  more  volatile  bituminous  coals  is  furthered 
by  the  use  of  mechanical  stokers.  (See  Chapter  11.)  Smokeless  com- 
bustion in  hand-fired  boilers  burning  high  volatile  solid  fuel  is  aided  (1) 
by  the  use  of  double  grates  with  down-draft  through  the  upper  grate,  (2) 
by  the  use  of  a  curtain  section  through  which  preheated  auxiliary  air  is 
introduced  over  the  fire  toward  the  rear  of  the  boiler,  and  (3)  by  the  intro- 
duction of  preheated  air  through  passages  at  the  front  of  the  boiler.  All 
three  methods  depend  largely  on  mixing  secondary  air  with  the  partially 
burned  volatiles  and  causing  this  mixture  to  pass  over  an  incandescent 
fuel  bed,  thus  tending  to  secure  more  complete  combustion  than  is  pos- 
sible in  boilers  without  such  provision. 

HEATING  SURFACE 

Boiler  heating  surface  is  that  portion  of  the  surface  of  the  heat  transfer 
apparatus  in  contact  with  the  fluid  being  heated  on  one  side  and  the  gas  or 
refractory  being  cooled  on  the  other  side.  Heating  surface  on  which  the 
fire  shines  is  known  as  direct  or  radiant  surface  and  that  in  contact  with 
hot  gases  only,  as  indirect  or  convection  surface.  The  amount  of  heating 
surface,  its  distribution  and  the  temperatures  on  either  side  thereof 
influence  the  capacity  of  any  boiler. 

Direct  heating  surface  is  more  valuable  than  indirect  per  square  foot 
because  it  is  subjected  to  a  higher  temperature  and  also,  in  the  case  of 
solid  fuel,  because  it  is  in  position  to  receive  the  full  radiant  energy  of  the 
fuel  bed.  The  heat  transfer  capacity  of  a  radiant  heating  surface  may  be 
as  high  as  6  to  8  times  that  of  an  indirect  surface.  This  is  one  of  the 
reasons  why  the  water  legs  of  some  boilers  have  been  extended,  especially 
in  the  case  of  stoker  firing  where  the  extra  amount  of  combustion  chamber 
secured  by  an  extension  of  the  water  legs  is  important.  For  the  same 
reason,  care  should  be  exercised  in  building  a  refractory  combustion 
chamber  in  an  oil-burning  boiler  so  as  not  to  screen  any  more  of  this 
valuable  surface  with  refractories  than  is  necessary  for  good  combustion. 

The  effectiveness  of  the  heating  surface  depends  on  its  cleanliness,  its 
location  in  the  boiler,  and  the  shape  of  the  gas  passages.  Investigations1 
by  the  U.  S.  Bureau  of  Mines  show  that: 

1.  A  boiler  in  which  the  heating  surface  is  arranged  to  give  long  gas  passages  of  small 
cross-section  will  be  more  efficient  than  a  boiler  in  which  the  gas  passages  are  short  and  of 
larger  cross-section. 

2.  The  efficiency  of  a  water  tube  boiler  increases  as  the  free  area  between  individual 
tubes  decreases  and  as  the  length  of  the  gas  pass  increases. 

3.  By  inserting  baffles  so  that  the  heating  surface  is  arranged  in  series  with  respect  to 
the  gas  flow,  the  boiler  efficiency  will  be  increased. 

The  area  of  the  gas  passages  must  not  be  so  small  as  to  cause  excessive 
resistance  to  the  flow  of  gases  where  natural  draft  is  employed. 

Heat  Transfer  Rates 

Practical  rates  of  heat  transfer  in  heating  boilers  will  average  about 
3300  Btu  per  sq  ft  per  hour  for  hand-fired  boilers  and  4000  Btu  per  sq  ft 


"See  U.  5.  Bureau  of  Mines  Bulletin  No.  18,  The  Transmission  of  Heat  into  Steam  Boilers. 

247 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 

per  hour  for  mechanically  fired  boilers  when  operating  at  design  load. 
When  operating  at  maximum  load2  these  values  will  run  between  5000  and 
6000  Btu  per  sq  ft  per  hour.  Boilers  operating  under  favorable  conditions 
at  the  above  heat  transfer  rates  will  give  exit  gas  temperatures  that  are 
considered  consistent  with  good  practice. 

TESTING  AND  RATING  CODES 

The  Society  has  adopted  three  solid  fuel  testing  codes,  a  solid  fuel 
rating  code  and  an  oil  fuel  testing  code.  A.S.H.V.E.  Standard  and  Short 
Form  Heat  Balance  Codes  for  Testing  Low-Pressure  Steam  Heating 
Solid  Fuel  Boilers — Codes  1  and  2 — (Revision  of  June  1929)8,  are  intended 
to  provide  a  method  for  conducting  and  reporting  tests  to  determine  heat 
efficiency  and  performance  characteristics.  A.S.H.V.E.  Performance 
Test  Code  for  Steam  Heating  Solid  Fuel  Boilers— Code  No.  3 — (Edition  of 
1929)8  is  intended  for  use  with  A.S.H.V.E.  Code  for  Rating  Steam  Heating 
Solid  Fuel  Hand-Fired  Boilers4.  The  object  of  this  test  code  is  to  specify 
the  tests  to  be  conducted  and  to  provide  a  method  for  conducting  and 
reporting  tests  to  determine  the  efficiencies  and  performance  of  the  boiler. 
The  A.S.H.V.E.  Standard  Code  for  Testing  Steam  Heating  Boilers 
Burning  Oil  Fuel5  is  intended  to  provide  a  standard  method  for  con- 
ducting and  reporting  tests  to  determine  the  heating  efficiency  and  per- 
formance characteristics  when  oil  fuel  is  used  with  steam  heating  boilers. 

Steel  Heating  Boilers  Ratings 

The  Steel  Heating  Boiler  Institute  has  adopted  a  method  for  the  rating  of 
low  pressure  boilers  based  on  their  physical  characteristics  and  expressed 
in  square  feet  of  steam  or  water  radiation  or  in  Btu  per  hour  as  given  in 
Table  2.  The  following  requirements  are  included  in  this  Code: 

1.  One  square  foot  of  steam  radiation  is  to  be  considered  equal  to  the  emission  of 
240  Btu  per  hour  and  one  square  foot  of  water  radiation  is  to  be  considered  equal  to 
emission  of  150  Btu  per  hour. 

2.  The  rating  of  a  boiler  expressed  in  square  feet  of  steam  radiation  in  which  solid  fuel 
hand  fired  is  used  is  based  on  the  amount  equal  to  14  times  the  heating  surface  of  the 
boiler  in  square  feet. 

3.  The  rating  of  a  boiler  expressed  in  square  feet  of  steam  radiation  in  which  solid  fuel 
mechanically  fired,  or  in  which  oil  or  gas  is  burned,  is  based  on  the  amount  equal  to 
17  times  the  heating  surface  of  the  boiler  in  square  feet. 

4.  Heating  surface  is  to  be  expressed  in  square  feet  and  include  those  surfaces  in  the 
boiler  which  are  exposed  to  the  products  of  combustion  on  one  side  and  water  on  the 
other.     In  measuring  surfaces,  the  outer  tube  areas  are  to  be  considered.     When  a 
boiler  has  the  water  leg  height  increased  the  heating  surface  noted  in  the  published 
ratings  are  not  to  be  increased. 

5.  A  grate  area  is  to  be  considered  as  an  area  of  the  grate  surface  expressed  in  square 
feet  and  measured  in  the  plane  of  the  top  surface  of  the  grate.    For  double  grate  boilers 
the  grate  surface  is  to  be  considered  as  the  area  of  the  upper  grate  plus  one-quarter  of  the 
area  of  the  lower  grate. 

6.  The  grate  area  of  a  boiler  for  rating  as  determined  in  No.  2  is  to  be  not  less  than 
that  determined  by  the  following  formulae: 

For  boilers  with  ratings  1800  sq  ft  to  4000  sq  ft  of  steam  radiation: 

Grate  Area  =   ^/Catalogue  Rating  (in  square  feet  steam  radiation)  —  200      Q\ 


^/ 
M 


aFor  definitions  of  design  load  and  maximum  load  see  pages  251  and  252. 
'See  A.S.H.V.E.  TRANSACTIONS,  Vol.  35,  1929,  p.  12.   Also  Chapter  45. 
4See  A.S.H.V.E.  TRANSACTIONS,  Vol.  36,  1930,  p.  35.   Also  Chapter  45. 
*See  A.S.H.V.E.  TRANSACTIONS,  Vol.  37,  1931,  p.  23*   Also  Chapter  45. 

24S 


CHAPTER  13.   HEATING  BOILERS 


TABLE  2.    STANDARD  STEEL  HEATING  BOILER  RATINGS'* 


HAND  FIRED  CAPACITY  RATING 


MECHANICALLY  FIRED  CAPACITY  RATING 


Steam 
Radiation 
SqFt 

Water 
Radiation 
SqFt 

Btu  per  Hr 

Heating 
Surface 
SqFt 

Grate 
Area 
SqFt 

Steam 
Radiation 
SqFt 

w  .        :                              Furnace  Volume 
Rg&j      Btu^rHr        *££-&* 
^Ft    :                                  CuFt 

1,800 

2,880 

432,000 

129 

7.9  '    2,190  !    3,500  ,        525,600   ,          15.7 

2,200 

3,520 

528,000 

158 

8.9       2,680 

4,280  j        643,200              19.2 

2,600 

4,160 

624,000 

186 

9.7 

3,160       5,050  !        75S,400   ,          22.6 

3,000 

4,800 

720,000 

215 

10.5       3,650       5,840          876.000             26.1 

3,500 

5,600 

840,000 

250 

11.4  ,    4,250       6,800        1,020,000             30.4 

4,000 

6,400 

960,000 

286 

12.2  j    4,860       7,770  ;     1,166,400             34.8 

4,500 

7,200 

1,080,000 

322 

13.4 

5,470  !    8,750        1,312,800             39.1 

5,000 

8,000 

1,200,000 

358 

14.5 

6,080  :    9,720  i      1,459,200             43.5 

6,000 

9,600 

1,440,000 

429 

16.4 

7,290 

11,660        1,749,600 

52.1 

7,000 

11,200 

1,680,000 

500 

18.1 

8,500     13,600  i     2,040,000             60.8 

8,500 

13,600 

2,OW,000 

608 

20.5 

10,330 

16,520       2,479,200 

73.8 

10,000 

16,000 

2,400,000 

715 

22.5 

12,150     19,440 

2,916.000 

86.8 

12,500 

20,000 

3,000,000 

893 

25.6 

15,180     24,280 

3,643,200 

108.5 

15,000 

24,000 

3,600,000 

1,072 

28.4 

18,220 

29,150  i     4,372,800 

130.2 

17,500 

28,000 

4,200,000 

1,250 

30.9 

21,250 

34,000 

5T100,000 

151.8 

20,000 

32,000 

4,800,000 

1,429 

33.2 

24,290 

38,860 

5,829,600 

173.5 

25,000 

40,000 

6,000,000 

1,786 

37.4 

30,360 

48,570 

7,286,400 

216.9 

30,000 

48,000 

7,200,000 

2,143 

41.2 

36,430 

58,280 

8,743,200 

260.3 

35,000 

56,000 

8,400,000 

2,500 

44.7 

42,500 

68,000 

10,200,000 

303.6 

aAdopted  by  the  Steel  Heating  Boiler  Institute  in  cooperation  with  the  Bureau  of  Standards,  United  States 
Department  of  Commerce  Simplified  Practice  Recommendation  R  157-S5. 

For  boilers  with  ratings  4000  sq  ft  of  steam  radiation  and  larger: 


Grate  Area 


V  Catalogue  Rating  (in  square  feet  steam  radiation)  —  1500 
16.8 


7.  The  volume  for  furnaces  in  which  solid  fuel  is  burned  is  to  be  considered  as  the 
cubical  content  of  the  space  between  the  bottom  of  the  fuel  bed  and  the  first  plane  of 
entry  into  or  between  the  tubes.  Volume  of  furnaces  in  which  pulverized  liquid  fuel  or 
gaseous  fuel  is  burned  are  to  be  considered  as  the  cubical  content  of  the  space  between 
the  hearth  and  the  first  plane  of  entry  into  or  between  the  tubes.    No  minimum  furnace 
volume  is  to  be  specified  for  mechanical  fired  boilers  burning  anthracite. 

8.  The  furnace  volume  for  a  boiler,  with  a  rating  as  determined  in  No.  3  in^which  oil, 
gas  or  bituminous  coal  stoker  fired  is  burned  is  not  to  be  less  than  one  cubic  foot  for 
every  140  sq  ft  of  steam  rating. 

9.  The  average  height  of  furnace  for  the  rating  determined  in  No.  3  in  which  bitu- 
minous coal,  stoker  fired  is  burned  is  not  to  be  less  than  that  determined  graphically  in 
Fig.  1  or  mathematically  by  the  following  formula: 


(3) 


where 

H  —  average  furnace  height,  inches  as  determined  by  the  following  formula; 

12F        12F 


H 


WL 


R  =  stoker  fired  boiler  rating,  square  foot  steam  radiation. 

A  =  plan  area  of  firebox,  square  feet  measured  at  the  bottom  of  the  fuel  bed. 

F  =  furnace  volume,  cubic  feet. 

249 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 


W  =  average  width  of  furnace,  measured  at  the  bottom  of  the  fuel  bed,  feet. 
L  —  length  of  furnace,  feet.    If  the  furnace  is  longer  than  the  fuel  bed  or  contains  a 
bridge  wall,  the  total  length  of  the  furnace  may  be  used  except  that  this  length 
is  not  to  exceed  2  J£  W. 

BOILER  OUTPUT 

Boiler  output  as  defined  in  A.S.H.V.E.  Performance  Test  Code  for 
Steam  Heating  Solid  Fuel  Boilers  (Code  No.  3)  is  the  quantity  of  heat 
available  at  the  boiler  nozzle  with  the  boiler  normally  insulated.  It 
should  be  based  on  actual  tests  conducted  in  accordance  with  this  code. 
This  output  is  usually  stated  in  Btu  and  in  square  feet  of  equivalent  heat- 
ing surface  (radiation).  According  to  the  A.S.H.V.E.  Standard  Code  for 


PLAN  AREA  OF  FURNACE,  SQUARE  FEET 


FIG.  1.    FURNACE  HEIGHTS  FOR  STOKER  FIRED  BOILERS  AND  BITUMINOUS  COAL 
RATED  IN  SQUARE  FEET  STEAM  RADIATION 


Rating  Steam  Heating,  Solid  Fuel,  Hand-Fired  Boilers,  the  performance 
data  should  be  given  in  tabular  or  curve  form  on  the  following  items  for  at 
least  five  outputs  ranging  from  maximum  down  to  35  per  cent  of  maxi- 
mum: (1)  fuel  available,  (2)  combustion  rate,  (3)  efficiency,  (4)  draft 
tension,  (5)  flue  gas  temperature.  The  only  definite  restriction  placed  on 
setting  the  maximum  output  is  that  priming  shall  not  exceed  2  per  cent. 
These  curves  provide  complete  data  regarding  the  performance  of  the 
boiler  under  test  conditions.  Certain  other  pertinent  information,  such  as 
grate  area,  heating  surface  and  chimney  dimensions  is  desirable  also  in 
forming  an  opinion  of  how  the  boiler  will  perform  in  actual  service. 

The  output  of  large  heating  boilers  is  frequently  stated  in  terms  of 
boiler  horsepower  instead  of  in  Btu  per  hour  or  square  feet  of  equivalent 
radiation. 

250 


CHAPTER  13.   HEATING  BOILERS 


Boiler  Horsepower :  The  evaporation  of  34.5  Ib  of  water  per  hour 
from  and  at  212  F  which  is  equivalent  to  a  heat  output  of  970.2  X  34.5  = 
33,471.9  Btu  per  hour. 

Equivalent  Evaporation :  The  amount  of  water  a  boiler  would 
evaporate,  in  pounds  per  hour,  if  it  received  feed  water  at  212  F  and 
vaporized  it  at  this  same  temperature  and  at  atmospheric  pressure. 

It  is  usually  considered  that  10  sq  ft  of  boiler  heating  surface  will  pro- 
duce a  rated  boiler  horsepower.  A  rated  boiler  horsepower  in  turn 
can  carry  a  design  load  of  from  100  to  140  sq  ft  of  equivalent  radiation. 
It  is  apparent,  therefore,  that  1  sq  ft  of  boiler  heating  surface  can  carry  a 
design  load  of  from  10  to  14  sq  ft  of  equivalent  radiation,  or  somewhat 
more  if  the  boiler  is  forced  above  rating.  The  application  of  these  values 
is  discussed  under  the  heading  Selection  of  Boilers. 

BOILER  EFFICIENCY 

The  term  efficiency  as  used  for  guarantees  of  boiler  performance  is 
usually  construed  as  follows: 

1.  Solid  Fuels.    The  efficiency  of  the  boiler  alone  is  the  ratio  of  the  heat  absorbed  by 
the  water  and  steam  in  the  boiler  per  pound  of  combustible  burned  on  the  grate  to  the 
calorific  value  of  1  Ib  of  combustible  as  fired.    The  combined,  efficiency  of  boiler,  furnace 
and  grate  is  the  ratio  of  the  heat  absorbed  by  the  water  and  steam  in  the  boiler  per  pound 
of  fuel  as  fired  to  the  calorific  value  of  1  Ib  of  fuel  as  fired. 

2.  Liquid  Fuels.    The  combined  efficiency  of  boiler,  furnace  and  burner  is  the  ratio  of 
the  heat  absorbed  by  the  water  and  steam  in  the  boiler  per  pound  of  fuel  to  the  calorific 
value  of  1  Ib  of  fuel. 

Solid  fuel  boilers  usually  show  an  efficiency  of  50  to  75  per  cent  when 
operated  under  favorable  conditions  at  their  rated  capacities.  Infor- 
mation on  the  combined  efficiencies  of  boiler,  furnace  and  burner  has 
resulted  from  research  conducted  at  Yale  University  in  cooperation  with 
the  A.S.H.V.E,  Research  Laboratory  and  the  American  Oil  Burner 
Association*. 

SELECTION  OF  BOILERS 

Estimated  Design  Load :  The  load,  stated  in  Btu  per  hour  or  equiva- 
lent direct  radiation,  as  estimated  by  the  purchaser  for  the  conditions  of 
inside  and  outside  temperature  for  which  the  amount  of  installed  radiation 
was  determined  is  the  sum  of  the  heat  emission  of  the  radiation  to  be 
actually  installed  plus  the  allowance  for  the  heat  loss  of  the  connecting 
piping  plus  the  heat  requirement  for  any  apparatus  requiring  heat  con- 
nected with  the  system  (A.S.H.V.E.  Standard  Code  for  Rating  Steam 
Heating  Solid  Fuel  Hand-Fired  Boilers— Edition  of  April,  1932). 

The  estimated  design  load  is  the  sum  of  the  following  three  items7: 

1.  The  estimated  heat  emission  in  Btu  per  hour  of  the  connected  radiation  (direct, 
indirect  or  central  fan)  to  be  installed. 

2.  The  estimated  maximum  heat  in  Btu  per  hour  required  to  supply  water  heaters 
or  other  apparatus  to  be  connected  to  the  boiler. 


6Study  of  the  Characteristics  of  Oil  Burners  and  Heating  Boilers,  by  L.  E.  Seeley  and  E.  J.  Tavanlar 
(A.S.H.V.E.  TRANSACTIONS,  Vol.  37, 1931,  p.  517),  A  Study  of  Intermittent  Operation  of  Oil  Burners,  by  L. 
E.  Seeley  and  J.  H.  Powers  (A.S.H.V.E.  TRANSACTIONS,  Vol.  38,  1932,  p.  317). 

7A.S.H.V.E.  Code  of  Minimum  Requirements  for  the  Heating  and  Ventilation  of  Buildings  (Edition 
of  1929). 

251 


HEATING   VENTILATING   Am  CONDITIONING   GUIDE  1938 

3.  The  estimated  heat  emission  in  Btu  per  hour  of  the  piping  connecting  the  radiation 
and  other  apparatus  to  the  boiler. 

Estimated  Maximum  Load :  Construed  to  mean  the  load  stated  in 
Btu  per  hour  or  the  equivalent  direct  radiation  that  has  been  estimated  by 
the  purchaser  to  be  the  greatest  or  maximum  load  that  the  boiler  will  be 
called  upon  to  carry.  (A.S.H.V.E.  Standard  Code  for  Rating  Steam 
Heating  Solid  Fuel  Hand-Fired  Boilers— Edition  of  April,  1932.) 

The  estimated  maximum  load  is  given  by8: 

4.  The  estimated  increase  in  the  normal  load  in  Btu  per  hour  due  to  starting  up  cold 
radiation.    This  percentage  of  increase  is  to  be  based  on  the  sum  of  Items  1,  2  and  3 
and  the  heating-up  factors  given  in  Table  3. 

TABLE  3.    WARMING-UP  ALLOWANCES  FOR  Low  PRESSURE  STEAM  AND 
HOT  WATER  HEATING  BoiLERsai  bi c 


DESIGN  LOAD  (REPRESENTING  STJMMA/TION  OF  ITEMS  1,  2,  AND  3,d 

PESCENTAOE  CAPACITY  TO  ADD 
FOR  WABMINO  UP 

Btu  per  Hour 

Equivalent  Square  Feet  of  Radiation* 

Up  to  100,000 
100,000  to  200,000 
200,000  to  600,000 
600,000  to  1,200,000 
1,200,000  to  1,800,000 
Above  1,800,000 

Up  to  420 
420  to  840 
840  to  2500 
2500  to  5000 
5000  to  7500 
Above  7500 

65 
60 
55 
50 
45      . 
40 

aThis  table  is  taken  from  the  A.S.H.V.E.  Code  of  Minimum  Requirements  for  the  Heating  and  Venti- 
lation of  Buildings,  except  that  the  second  column  has  been  added  for  convenience  in  interpreting  the  design 
load  in  terms  of  equivalent  square  feet  of  radiation. 

bSee  also  Time  Analysis  in  Starting  Heating  Apparatus,  by  Ralph  C.  Taggert  (A.S.H.V.E.  TRANSAC- 
TIONS, Vol.  19, 1913,  p.  292);  Report  of  A.S.H.V.E.  Continuing  Committee  on  Codes  for  Testing  and  Rating 
Steam  Heating  Solid  Fuel  Boilers  (A.S.H.V.E.  TRANSACTIONS,  Vol.  36,  1930,  p.  35) ;  Selecting  the  Right 
Size  Heating  Boiler,  by  Sabin  Crocker  (Heating,  Piping  and  Air  Conditioning,  March,  1932). 

cThis  table  refers  to  hand-fired,  solid  fuel  boilers.  A  factor  of  20  per  cent  over  design  load  is  adequate 
when  automatically-fired  fuels  are  used  (see  Fig.  3). 

d240  Btu  per  square  foot. 

Other  things  to  be  considered  are: 

5.  Efficiency  with  hard  or  soft  coal,  gas,  or  oil  firing,  as  the  case  may  be. 

6.  Grate  area  with  hand-fired  coal,  or  fuel  burning  rate  with  stokers,  oil,  or  gas. 

7.  Combustion  space  in  the  furnace. 

8.  Type  of  heat  liberation,  whether  continuous  or  intermittent,  or  a  combination  of 
both. 

9.  Miscellaneous  items  consisting  of  draft  available,  character  of  attendance,  pos- 
sibility of  future  extension,  possibility  of  breakdown  and  headroom  in  the  boiler  room. 

Radiation  Load 

The  connected  radiation  (Item  1)  is  determined  by  calculating  the^heat 
losses  in  accordance  with  data  given  in  Chapters  5,  6  and  7,  and  dividing 
by  240  to  change  to  square  feet  of  equivalent  radiation  as  explained  in 
Chapter  14.  For  hot  water,  the  emission  commonly  used  is  150  Btu  per 
square  foot,  but  the  actual  emission  depends  on  the  temperature  of  the 
medium  in  the  heating  units  and  of  the  surrounding  air.  (See  Chapter  14.) 

Although  it  is  customary  to  use  the  actual  connected  load  in  equivalent 
square  feet  of  radiation  for  selecting  the  size  of  boiler,  this  connected  load 
usually  represents  a  reserve  in  heating  capacity  to  provide  for  infiltration 
in  the  various  spaces  of  the  building  to  be  heated,  which  reserve,  however, 

8Loc.  Cit.  Note  7. 

252 


CHAPTER  13.   HEATING  BOILERS 


is  not  in  use  at  all  places  at  the  same  time,  or  in  any  one  place  at  all  times. 
For  a  further  discussion  of  this  subject  see  Chapter  6. 

Hot  Water  Supply  Load 

When  the  hot  water  supply  (Item  2)  is  heated  by  the  building  heating 
boiler,  this  load  must  be  taken  into  consideration  in  sizing  the  boiler.  The 


0.6         60 


^0.3   §  5   |5|4.5 

OK  <       |j 

So-2  ^40   *  105  a 

LI   i.it 


1000 


3OOO 


OUTPUT.  SQ.  FT,  EQUIVALENT  STEAM  RADIATION   (240  BTU   PER  3Q.  FT.) 

BOILER   DATA-      CRATE  AREA.SQ.FT.  16-0  FUEL-BITUMINOUS    3/4-  LUMP 

HEATING  SURFACE.SQ  FT.  254  ANALYSIS-   VOLATILE  MATTER       34.687. 

WEIGHT,  LB.                            0160  FIXED  CARBON             35-44 

FUEL  CAPACITY.  LB.              63.  ASH                                       9.97 

FUEL  AVAIL  ABLE,  LB.           414.  SULPHUR                             2.«6 

.      io 


FIG  2     TYPICAL  PERFORMANCE  CURVES  FOR  A  36-iN.  CAST-IRON  SECTIONAL  STEAM 

HEATING  BOILER,  BASED  ON  THE  A.S.H.V.E.  CODE  FOR  RATING  STEAM 

HEATING  SOLID  FUEL  HAND-FIRED  BOILERS 

allowance  to  be  made  will  depend  on  the  amount  of  water  heated  and  its 
temperature  rise.  A  good  approximation  is  to  add  4  sq  ft  of  equivalent 
radiation  for  each  gallon  of  water  heated  per  hour  through  a  temperature 
range  of  100  F.  For  more  specific  information,  see  Chapter  43. 

Piping  Tax  (Item  3) 

It  is  common  practice  to  add  a  flat  percentage  allowance  to  the 
equivalent  connected  radiation  to  provide  for  the  heat  loss  from  bare  and 
covered  pipe  in  the  supply  and  return  lines.  The  use  of  a  flat  allowance  of 
25  per  cent  for  steam  systems  and  35  per  cent  for  hot  water  systems  is 
preferable  to  ignoring  entirely  the  load  due  to  heat  loss  from  the  supply 

253 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

and  return  lines,  but  better  practice,  especially  when  there  is  much  bare 
pipe,  is  to  compute  the  emission  from  both  bare  and  covered  pipe  surface 
in  accordance  with  data  in  Chapter  39.  A  chart  is  shown  in  Fig.  3  indicat- 
ing percentage  allowances  for  piping  and  warming-up  which  are  applic- 
able to  automatically-fired  heating  plants  using  steam  radiation.  With 
direct  radiation  served  by  bare  supply  and  return  piping  the  percentages 
may  be  higher  than  those  stated,  while  in  the  case  of  unit  heaters  where 
the  output  is  concentrated  in  a  few  locations/  the  piping  tax  may  be 
10  per  cent  or  less. 


10  12  14 

NET  LOAD,  STEAM  RADIATION,  THOUSAND  SQ  FT 


18 


FIG.  3.    PERCENTAGE  ALLOWANCE  FOR  PIPING  AND  WARMING-UP 


Warming-Up  Allowance 

The  warming-up  allowance  represents  the  load  due  to  heating  the  boiler 
and  contents  to  operating  temperature  and  heating  up  cold  radiation  and 
piping.  (See  Item  4.)  The  factors  to  be  used  for  determining  the 
allowance  to  be  made  should  be  selected  from  Table  3  and  should  be 
applied  to  the  estimated  design  load  as  determined  by  Items  1,  2  and  3. 
While  in  every  case  the  estimated  maximum  load  will  exceed  the  design 
load  if  adequate  heating  response  is  to  be  achieved,  there  is  however,  no 
object  in  over-estimating  the  allowances,  as  the  only  effect  would  be  to 
reduce  the  time  of  warming-up  by  a  few  minutes.  Otherwise,  it  might 
result  in  firing  the  boiler  unduly  and  increasing  the  cost  of  operation. 

Performance  Curves  for  Boiler  Selection 

In  the  selection  of  a  boiler  to  meet  the  estimated  load,  the  A.S.H.V.E. 


Standard  Code  for  Rating  Steam  Heating  Solid  Fuel  Hand-Fired  Boilers 
recommends  the  use  of  performance  curves  based  on  actual  tests  con- 
ducted in  accordance  with  the  A.S.H.V.E.  Performance  Test  Code  for 
Steam  Heating  Solid  Fuel  Boilers  (Code  No.  3),  similar  to  the  typical 
curves  shown  in  Fig.  2.  It  should  be  understood  that  performance  data 
apply  to  test  conditions  and  that  a  reasonable  allowance  should  be  made 
for  decreased  output  resulting  from  soot  deposit,  poor  fuel  or  inefficient 
attention. 

254 


CHAPTER  13.   HEATING  BOILERS 


Selection  Based  on  Heating  Surface  and  Grate  Area 

Where  performance  curves  are  not  available,  a  good  general  rule  for 
conventionally-designed  boilers  is  to  provide  1  sq  ft  of  boiler  heating 
surface  for  each  14  sq  ft  of  equivalent  radiation  (240  Btu  per  square  foot) 
represented  by  the  design  load  consisting  of  connected  radiation,  piping 
tax  and  domestic  water  heating  load.  As  stated  in  the  section  on  Boiler 
Output,  this  is  equivalent  to  allowing  10  sq  ft  of  boiler  heating  surface  per 
boiler  horsepower.  In  this  case  it  is  assumed  that  the  maximum  load 
including  the  warming-up  allowance  will  be  provided  for  by  operating  the 
boiler  in  excess  of  the  design  load,  that  is,  in  excess  of  the  100  per  cent 
rating  on  a  boiler-horsepower  basis. 

Due  to  the  wide  variation  encountered  in  manufacturers'  ratings  for 
boilers  of  approximately  the  same  capacity,  it  is  advisable  to  check  the 
grate  area  required  for  heating  boilers  burning  solid  fuel  by  means  of  the 
following  formula: 

TT 

G  =  CXFXE  (4) 

where 

G  =  grate  area,  square  feet. 

H  =  required  total  heat  output  of  the  boiler,  Btu  per  hour  (see  Selection  of  Boilers, 

p.  251). 
C  —  combustion  rate  in  pounds  of  dry  coal  per  square  foot  of  grate  area  per  hour, 

depending  on  the  kind  of  fuel  and  size  of  boiler  as  given  in  Table  1. 
F  —  calorific  value  of  fuel,  Btu  per  pound. 
E  =•  efficiency  of  boiler,  usually  taken  as  0.60. 

Example  1.  Determine  the  grate  area  for  a  required  heat  output  of  the  boiler  of 
500,000  Btu  per  hour,  a  combustion  rate  of  6  Ib  per  hour,  a  calorific  value  of  13,000  Btu 
per  pound,  and  an  efficiency  of  60  per  cent. 


The  boiler  selected  should  have  a  grate  area  not  less  than  that  deter- 
mined by  Formula  4.  With  small  boilers  where  it  is  desired  to  provide 
sufficient  coal  capacity  for  approximately  an  eight-hour  firing  period  plus 
a  20  per  cent  reserve  for  igniting  a  new  charge,  more  grate  area  may  be 
required  depending  upon  the  depth  of  the  fuel  pot. 

Selection  of  Steel  Heating  Boilers 

Boiler  ratings  previously  described  under  the  Steel  Heating  Boiler 
Institute's  Boiler  Rating  Code  are  intended  to  correspond  with  the  esti- 
mated design  load  based  on  the  sum  of  items  1,  2  and  3  outlined  on  pages 
252  and  253.  Insulated  residence  type  boilers  for  oil  or  gas  may  carry 
a  net  load  expressed  in  square  feet  of  steam  radiation  of  not  more  than 
17  times  the  square  feet  of  heating  surface  in  the  boiler,  provided  the 
boiler  manufacturer  guarantees  the  boiler  to  be  capable  of  operating  at  a 
maximum  output  of  not  less  than  150  per  cent  of  net  load  rating  with  over- 
all efficiency  of  not  less  than  75  per  cent  with  at  least  two  different  makes 
of  each  type  of  standard  commercial  burner  recommended  by  the  boiler 
manufacturer.  If  the  heat  loss  from  the  piping  system  exceeds  20  per  cent 
of  the  installed  radiation,  the  excess  is  to  be  considered  as  a  part  of  the  net 
load. 

255 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


When  the  estimated  heat  emission  of  the  piping  (connecting  radiation, 
and  other  apparatus  to  the  boiler)  is  not  known  the  net  load  to  be  con- 
sidered for  the  boiler  may  be  determined  from  Table  4. 

Selection  of  Gas-Fired  Boilers 

Gas-heating  appliances  should  be  selected  in  accordance  with  the 
percentage  allowances  given  in  Fig.  3.  These  factors  are  for  thermo- 
statically-controlled systems;  in  case  manual  operation  is  desired,  a 
warming-up  allowance  of  100  per  cent  is  recommended  by  the  A.G.A. 
A  gas  boiler  selected  by  the  use  of  the  A.G.A.  factors  will  be  the  minimum 

TABLE  4.    BOILER  RATINGS  BASED  ON  NET  LoADa 


HAJTD  FIRED  RATINGS 

MECHANICALLY  FIRED  RATINGS 

Steam  Radiation  Sq  Ft 

Net  Loadb 
Steam  Radiation  Sq  Ft 

Steam  Radiation  Sq  Ft 

Net  Loadb 
Steam  Radiation  Sq  Ft 

1,800 

1,389 

2,190 

1,695 

2,200 

1,702 

2,680 

2,089 

2,600 

2,020 

3,160 

2,461 

3,000 

2,335 

3,650 

2,853 

3,500 

2,732 

4,250 

3,335 

4,000 

3,135 

4,860 

3,830 

4,500 

3,540' 

5,470 

4,330 

5,000 

3,945 

6,080 

4,834 

6,000 

4,770 

7,290 

5,850 

7,000 

5,608 

8,500 

6,885 

8,500 

6,885 

10,330 

8,490 

10,000 

8,197 

12,150 

10,125 

12,500 

10,417 

15,180 

12,650 

15,000 

12,500 

18,220 

15,183 

17,500 

14,584 

21,250 

17,708 

20,000 

16,667 

24,290 

20,242 

25,000 

20,834 

30,360 

25,300 

30,000 

25,000 

36,430 

30,359 

35,000 

29,167 

42,500 

35,417 

aAdopted  by  the  Steel  Heating  Boiler  Institute  in  cooperation  with  the  Bureau  of  Standards ,  United  States 
Department  of  Commerce  Simplified  Practice  Recommendation  R  157-35. 

bThe  net  load  is  made  up  by  the  sum  of  the  estimated  design  load,  items  1  and  2  (pages  252  and  253).  All 
net  loads  are  expressed  in  70  F.  For  hand  fired  boiler  ratings  less  than  1800  sq  ft  of  steam  or  2880  sq.  ft  of 
water  and  mechanically  fired  boiler  ratings  of  2190  sq  ft  of  steam  or  3500  sq  ft  of  water,  apply  the  factor 
1.3  to  the  net  load  to  determine  the  boiler  size.  For  water  boilers  use  the  equivalent  net  load  for  steam 
boilers  of  similar  physical  size. 

size  boiler  which  can  carry  the  load.  From  a  fuel  economy  standpoint,  it 
may  be  advisable  to  select  a  somewhat  larger  boiler  and  then  throttle  the 
gas  and  air  adjustments  as  required.  This  will  tend  to  give  a  low  stack 
temperature  with  high  efficiency  and  at  the  same  time  provide  reserve 
capacity  in  case  the  load  is  under-estimated  or  more  is  added  in  the  future. 

Conversions 

The  conversion  of  a  coal  or  oil  boiler  to  gas  burning  is  simpler  than  the 
reverse  since  little  furnace  volume  need  be  provided  for  the  proper  com- 
bustion of  gas.  When  a  solid  fuel  boiler  of  500  sq  ft  (or  less)  capacity  is 
converted  to  gas  burning,  the  necessary  gas  heat  units  should  be  approxi- 
mately double  the  connected  load.  The  presumption  for  a  conversion 
job  is  that  the  boiler  is  installed  and  probably  will  not  be  made  larger; 

256 


CHAPTER  13.   HEATING  BOILERS 


therefore,  it  is  a  matter  of  setting  a  gas-burning  rate  to  obtain  best  results 
with  the  available  surface.  Assuming  a  combustion  efficiency  of  75  per 
cent  for  a  conversion  installation  the  boiler  output  would  be  2  X  0.75 
=  1.5  times  the  connected  load,  which  allows  50  per  cent  for  piping  tax 
and  pickup.  In  converting  large  boilers,  the  determination  of  the  re- 
quired Btu  input  should  not  be  done  by  an  arbitrary  figure  or  factor  but 
should  be  based  on  a  detailed  consideration  of  the  requirements  and 
characteristics  of  the  connected  load. 

An  efficient  conversion  installation  depends  upon  the  proper  size  of 
flue  connection.  Often  the  original  smoke  breeching  between  the  boiler 
and  chimney  is  too  large  for  gas  firing,  and  in  this  case,  flue  orifices  can  be 
used.  They  are  discs  provided  with  an  opening  of  the  size  for  the  gas 
input  used  in  this  boiler.  The  size  should  be  based  on  1  sq  in.  of  flue  area 
for  each  7500  hourly  Btu  input. 

If  dampers  are  found  in  the  breeching  they  should  be  locked  in  position 
so  that  they  will  not  interfere  with  the  normal  operation  of  the  gas  burners 
at  maximum  flow.  In  the  case  of  large  boiler  conversions,  automatic 
damper  regulators  proportion  the  position  of  the  flue  dampers  to  the 
amount  of  gas  flowing  and  may  be  substituted  for  existing  dampers. 
Generally  in  residence  conversions  automatic  dampers  are  not  of  the 
proportioning  type  but  close  the  flue  during  the  off  periods  of  the  gas 
burners.  Automatic  shutoff  dampers  should  be  located  between  the 
backdraft  diverter  and  the  chimney  flue.  Automatic  dampers  are  usually 
designed  to  operate  with  electric  contact  mechanism,  but  frequently  an 
arrangement  is  utilized  which  functions  with  mechanical  fluid  or  gas 
pressure. 

Physical  Limitations 

As  it  will  usually  be  found  that  several  boilers  will  meet  the  speci- 
fications, the  final  selection  of  the  boiler  may  be  influenced  by  other  con- 
siderations, some  of  which  are: 

1.  Dimensions  of  boiler. 

2.  Durability  under  service. 

3.  Convenience  in  firing  and  cleaning. 

4.  Adaptability  to  changes  in  fuel  and  kind  of  attention. 

5.  Height  of  water  line. 

In  large  installations,  the  use  of  several  smaller  boiler  units  instead  of 
one  larger  one  will  obtain  greater  flexibility  and  economy  by  permitting 
the  operation,  at  the  best  efficiency,  of  the  required  number  of  units 
according  to  the  heat  requirements. 

Space  Limitations 

Boiler  rooms  should,  if  possible,  be  situated  at  a  central  point  with 
respect  to  the  building  and  should  be  designed  for  a  maximum  of  natural 
light.  The  space  in  front  of  the  boilers  should  be  sufficient  for  firing, 
stoking,  ash  removal  and  cleaning  or  renewal  of  flues,  and  should  be  at 
least  3  ft  greater  than  the  length  of  the  boiler  firebox. 

A  space  of  at  least  3  ft  should  be  allowed  on  at  least  one  side  of  every 
boiler  for  convenience  of  erection  and  for  accessibility  to  the  various 

257 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

dampers,  cleanouts  and  trimmings.  The  space  at  the  rear  of  the  boiler 
should  be  ample  for  the  chimney  connection  and  for  cleanouts.  With 
large  boilers  the  rear  clearance  should  be  at  least  3  ft  in  width. 

The  boiler  room  height  should  be  sufficient  for  the  location  of  boiler 
accessories  and  for  proper  installation  of  piping.  In  general  the  ceiling 
height  for  small  steam  boilers  should  be  at  least  3  ft  above  the  normal 
boiler  water  line.  With  vapor  heating,  especially,  the  height  above  the 
boiler  water  line  is  of  vital  importance. 

When  steel  boilers  are  used,  space  should  be  provided  for  the  removal 
and  replacement  of  tubes. 

CONNECTIONS  AND  FITTINGS 

The  velocity  of  flow  through  the  outlets  of  low  pressure  steam  heating 
boilers  should  not  exceed  15  to  25  fps  if  fluctuation  of  the  water  line  and 
undue  entrainment  of  moisture  are  to  be  avoided.  Steam  or  water  outlet 
connections  preferably  should  be  the  full  size  of  the  manufacturers' 
tapping  and  should  extend  vertically  to  the  maximum  height  available 
above  the  boiler.  For  gravity  circulating  steam  heating  systems,  it  is 
recommended  that  a  Hartford  Loop,  described  in  Chapter  16,  be  utilized 
in  making  the  return  connection. 

Particular  attention  should  be  given  to  fitting  connections  to  secure  con- 
formity with  the  A.S.MJS.  Boiler  Construction  Code  for  Low  Pressure 
Heating  Boilers.  Attention  is  called  in  particular  to  pressure  gage  piping, 
water  gage  connections  and  safety  valve  capacity. 

Steam  gages  should  be  fitted  with  a  water  seal  and  a  shut-off  consisting 
of  a  cock  with  either  a  tee  or  lever  handle  which  is  parallel  to  the  pipe 
when  the  cock  is  open.  Steam  gage  connections  should  be  of  copper  or 
brass  when  smaller  than  1  in.  I.P.S.9  if  the  gage  is  more  than  5  ft  from  the 
boiler  connection,  and  also  in  any  case  where  the  connection  is  less  than 
M  in.  I.P.S. 

Each  steam  or  vapor  boiler  should  have  at  least  one  water  gage  glass  and 
two  or  more  gage  cocks  located  within  the  range  of  the  visible  length  of  the 
glass.  The  water  gage  fittings  or  gage  cocks  may  be  direct  connected  to 
the  boiler,  if  so  located  by  the  manufacturer,  or  may  be  mounted  on  a 
separate  water  column.  No  connections,  except. for  combustion  regu- 
lators, drains  or  steam  gages,  should  be  placed  on  the  pipes  connecting 
the  water  column  and  the  boiler.  If  the  water  column  or  gage  glass  is  con- 
nected to  the  boiler  by  pipe  and  fittings,  a  cross,  tee  or  equivalent,  in  which 
a  deanout  plug  or  a  drain  valve  and  piping  may  be  attached,  should  be 
placed  in  the  water  connection  at  every  right-angle  turn  to  facilitate 
cleaning.  The  water  line  in  steam  boilers  should  be  carried  at  the  level 
specified  by  the  boiler  manufacturer. 

Safety  valves  should  be  capable  of  discharging  all  the  steam  that  can  be 
generated  by  the  boiler  without  allowing  the  pressure  to  rise  more  than 
5  Ib  above  the  maximum  allowable  working  pressure  of  the  boiler.  This 
should  be  borne  in  mind  particularly  in  the  case  of  boilers  equipped  with 
mechanical  stokers  or  oil  burners  where  the  amount  of  grate  area  has 
little  significance  as  to  the  steam  generating  capacity  of  the  boiler. 


'A3.M.E.  Code,  Identification  of  Piping  Systems. 

258 


CHAPTER  13.   HEATING  BOILERS 


Where  a  return  header  is  used  on  a  cast-iron  sectional  boiler  to  distribute 
the  returns  to  both  rear  tappings,  it  is  advisable  to  provide  full  size 
plugged  tees  instead  of  elbows  where  the  branch  connections  enter  the 
return  tappings.  This  facilitates  cleaning  sludge  from  the  bottom  of  the 
boiler  sections  through  the  large  plugged  openings.  An  equivalent  clean- 
out  plug  should  be  provided  in  the  case  of  a  single  return  connection. 

Blow-off  or  drain  connections  should  be  made  near  the  boiler  and  so 
arranged  that  the  entire  system  may  be  drained  of  water  by  opening  the 
drain  cock.  In  the  case  of  two  or  more  boilers  separate  blow-off  connec- 
tions must  be  provided  for  each  boiler  on  the  boiler  side  of  the  stop  valve 
on  the  main  return  connection. 

Water  service  connections  must  be  provided  for  both  steam  and  water 
boilers,  for  refilling  and  for  the  addition  of  make-up  water  to  boilers.  This 
connection  is  usually  of  galvanized  steel  pipe,  and  is  made  to  the  return 
main  near  the  boiler  or  boilers. 

For  further  data  on  pipe  connections  for  steam  and  hot  water  heating 
systems,  see  Chapters  16  and  17  and  thtA.S.M.E.  Boiler  Construction 
Code  for  Low  Pressure  Heating  Boilers. 

Smoke  Breeching  and  Chimney  Connections.  The  breeching  or  smoke 
pipe  from  the  boiler  outlet  to  the  chimney  should  be  air- tight  and  as  short 
and  direct  as  possible,  preference  being  given  to  long  radius  and  45-deg 
instead  of  90-deg  bends.  The  breeching  entering  a  brick  chimney  should 
not  project  beyond  the  flue  lining  and  where  practicable  it  should  be 
grouted  from  the  inside  of  the  chimney.  A  thimble  or  sleeve  grout 
usually  is  provided  where  the  breeching  enters  a  brick  chimney. 

Where  a  battery  of  boilers  is  connected  into  a  breeching  each  boiler 
should  be  provided  with  a  tight  damper.  The  breeching  for  a  battery 
of  boilers  should  not  be  reduced  in  size  as  it  goes  to  the  more  remote 
boilers.  Good  connections  made  to  a  good  chimney  will  usually  result  in 
a  rapid  response  by  the  boilers  to  demands  for  heat. 

ERECTION,  OPERATION,  AND  MAINTENANCE 

The  directions  of  the  boiler  manufacturer  always  should  be  read  before 
the  assembly  or  installation  of  any  boiler  is  started,  even  though  the 
contractor  may  be  familiar  with  the  boiler.  All  joints  requiring  boiler 
putty  or  cement  which  cannot  be  reached  after  assembly  is  complete 
must  be  finished  as  the  assembly  progresses. 

The  following  precautions  should  be  taken  in  all  installations  to  prevent 
damage  to  the  boiler: 

1.  There  should  be  provided  proper  and  convenient  drainage  connections  for  use  if 
the  boiler  is  not  in  operation  during  freezing  weather. 

2.  Strains  on  the  boiler  due  to  movement  of  piping  during  expansion  should  ^ be 
prevented  by  suitable  anchoring  of  piping  and  by  proper  provision  for  pipe  expansion 
and  contraction. 

3.  Direct  impingement  of  too  intense  local  heat  upon  any  part  of  the  boiler  surface, 
as  with  oil  burners,  should  be  avoided  by  protecting  the  surface  with  firebrick  or  other 
refractory  material. 

4.  Condensation  must  flow  back  to  the  boiler  as  rapidly  and  uniformly  as  possible. 
Return  connections  should  prevent  the  water  from  backing  out  of  the  boiler. 

5.  Automatic  boiler  feeders  and  low  water  cut-off  devices  which  shut  off  the  source 

259 


HEATING   VENTILATING  AIR  CONDITIONING   GUIDE  1938 

of  heat  if  the  water  in  the  boiler  falls  below  a  safe  level  are  recommended  for  boilers 
mechanically  fired. 

Boiler  Troubles 

A  complaint  regarding  boiler  operation  generally  will  be  found  to  be 
due  to  one  of  the  following: 

1.  The  boiler  fails  to  deliver  enough  heat.    The  cause  of  this  condition  may  be:  (a)  poor 
draft;  (&)  poor  fuel;  (c)  inferior  attention  or  firing;  (d)  boiler  too  small;  (e)  improper 
piping;  (f)  improper  arrangement  of  sections;  (g)  heating  surfaces  covered  with  soot; 
and  (h)  insufficient  radiation  installed. 

2.  The  water  line  is  unsteady.   The  cause  of  this  condition  may  be:    (a)  grease  and  dirt 
in  boiler;  (b)  water  column  connected  to  a  very  active  section  and,  therefore,  not 
showing  actual  water  level  in  boiler;  and  (d)  boiler  operating  at  excessive  output. 

3.  Water  disappears  from  gage  glass.    This  may  be  caused  by:     (a)  priming  due  to 
grease  and  dirt  in  boiler;  (b)  too  great  pressure  difference  between  supply  and  return 
piping  preventing  return  of  condensation;  (c)  valve  closed  in  return  line;  (d)  connection 
of  bottom  of  water  column  into  a  very  active  section  or  thin  waterway;  and  (e)  improper 
connections  between  boilers  in  battery  permitting  boiler  with  excess  pressure  to  push 
returning  condensation  into  boiler  with  lower  pressure. 

4.  Water  is  carried  over  into  steam  main.    This  may  be  caused  by:  (a)  grease  and  dirt 
in  boiler;  (b)  insufficient  steam  dome  or  too  small  steam  liberating  area;  (c)  outlet  con- 
nections of  too  small  area;  (d)  excessive  rate  of  output;  and  (e)  water  level  carried 
higher  than  specified. 

5.  Boiler  is  slow  in  response  to  operation  of  dampers.    This  may  be  due  to:  (a)  poor 
draft  resulting  from  air  leaks  into  chimney  or  breeching;  (b)  inferior  fuel;  (c)  inferior 
attention;  (d)  accumulation  of  clinker  on  grate;  and  (e)  boiler  too  small  for  the  load. 

6.  Boiler  requires^  too  frequent  cleaning  of  flues.    This  may  be  due  to:  (a)  poor  draft; 
(6)  smoky  combustion;  (c)  too  low  a  rate  of  combustion;  and  (d)  too  much  excess  air 
in  firebox  causing  chilling  of  gases. 

7.  Boiler  smokes  through  fire  door.    This  may  be  due  to:  (a)  defective  draft  in  chimney 
or  incorrect  setting  of  dampers;  (b)  air  leaks  into  boiler  or  breeching;  (c)  gas  outlet  from 
firebox  plugged  with  fuel;  (d)  dirty  or  clogged  flues;  and  (e)  improper  reduction  in 
breeching  size. 

Cleaning  Steam  Boilers 

All  boilers  are  provided  with  flue  clean-out  openings  through  which  the 
heating  surface^  can  be  reached  by  means  of  brushes  or  scrapers.  Flues 
of  solid  fuel  boilers  should  be  cleaned  often  to  keep  the  surfaces  free  of 
soot  or  ash.  Gas  boiler  flues  and  burners  should  be  cleaned  at  least  once 
a  year.  Oil  burning  boiler  flues  should  be  examined  periodically  to  deter- 
mine when  cleaning  is  necessary. 

The  grease  used  to  lubricate  the  cutting  tools  during  erection  of  new 
piping  systems  serves  as  a  carrier  for  sand  and  dirt,  with  the  result  that 
a  scum  of  fine  particles  and  grease  accumulates  on  the  surface  of  the 
water  in  all  new  boilers,  while  heavier  particles  may  settle  to  the  bottom 
of  the  boiler  and  form  sludge.  These  impurities  have  a  tendency  to  cause 
foaming,  preventing  the  generation  of  steam  and  causing  an  unsteady 
water  line. 

This  unavoidable  accumulation  of  oil  and  grease  should  be  removed 
by  blowing  off  the  boiler  as  follows:  If  not  already  provided,  install  a 
surface  blow  connection  of  at  least  1%  in.  nominal  pipe  size  with  outlet 
extended  to  within  18  in.  of  the  floor  or  to  sewer,  inserting  a  valve  in  line 
close  to  boiler.  Bring  the  water  line  to  center  of  outlet,  raise  steam  pres- 
sure and  while  fire  is  burning  briskly  open  valve  in  blow-off  line.  When 

260 


CHAPTER  13.   HEATING  BOILERS 


pressure  recedes  close  valve  and  repeat  process  adding  water  at  intervals 
to  maintain  proper  level.  As  a  final  operation  bring  the  pressure  in  the 
boiler  to  about  10  Ib,  close  blow-off,  draw  the  fire  or  stop  burner,  and  open 
drain  valve.  After  boiler  has  cooled  partly,  fill  and  flush  out  several  times 
before  filling  it  to  proper  water  level  for  normal  service.  The  use  of  soda, 
or  any  alkali,  vinegar  or  any  acid  is  not  recommended  for  cleaning  heating 
boilers  because  of  the  difficulty  of  complete  removal  and  the  possibility 
of  subsequent  injury,  after  the  cleaning  process  has  been  completed. 

Insoluble  compounds  have  been  developed  which  are  effective,  but 
special  instructions  on  the  proper  cleaning  compound  and  directions  for 
its  use  in  a  boiler,  as  given  by  the  boiler  manufacturer,  should  be  carefully 
followed. 

It  is  common  practice  when  starting  new  installations  to  discharge 
heating  returns  to  the  sewer  during  the  first  week  of  operation.  This 
prevents  the  passage  of  grease,  dirt  or  other  foreign  matter  into  the  boiler 
and  consequently  may  avoid  the  necessity  of  cleaning  the  boiler.  During 
the  time  the  returns  are  being  passed  to  the  sewer,  the  feed  valve  should 
be  cracked  sufficiently  to  maintain  the  proper  water  level  in  the  boiler. 

Care  of  Idle  Heating  Boilers 

Heating  boilers  are  often  seriously  damaged  during  summer  months 
due  chiefly  to  corrosion  resulting  from  the  combination  of  sulphur  from 
the  fuel  with  the  moisture  in  the  cellar  air.  At  the  end  of  the  heating 
season  the  following  precautions  should  be  taken: 

1.  All  heating  surfaces  should  be  cleaned  thoroughly  of  soot,  ash  and  residue,  and  the 
heating  surfaces  of  steel  boilers  should  be  given  a  coating  of  lubricating  oil  on  the  ore 
side. 

2.  All  machined  surfaces  should  be  coated  with  oil  or  grease. 

3.  Connections  to  the  chimney  should  be  cleaned  and  in  case  of  small  boilers  the  pipe 
should  be  placed  in  a  dry  place  after  cleaning. 

4.  If  there  is  much  moisture  in  the  boiler  room,  it  is  desirable  to  drain  the  boiler  to 
prevent  atmospheric  condensation  on  the  heating  surfaces  of  the  boiler  when  they  are 
below  the  dew-point  temperature.    Due  to  the  hazard  of  some  one  inadvertently  building 
a  fire  in  a  dry  boiler,  however,  it  is  safer  to  keep  the  boiler  filled  with  water.    A  hot  water 
system  usually  is  left  filled  to  the  expansion  tank. 

5.  The  grates  and  ashpit  should  be  cleaned. 

6.  Clean  and  repack  the  gage  glass  if  necessary. 

7.  Remove  any  rust  or  other  deposit  from  exposed  surfaces  by  scraping  with  a  wire 
brush  or  sandpaper.    After  boiler  is  thoroughly  cleaned,  apply  a  coat  of  preservative 
paint  where  required  to  external  parts  normally  painted. 

8.  Inspect  all  accessories  of  the  boiler  carefully  to  see  that  they  are  in  good  working 
order.     In  this  connection,  oil  all  door  hinges,  damper  bearings  and  regulator  parts. 

BOILER  INSULATION 

Insulation  for  cast-iron  boilers  is  of  two  general  types:  (1)  plastic 
material  or  blocks  wired  on,  cemented  and  covered  with  canvas  or  duck; 
and  (2)  blocks,  sheets  or  plastic  material  covered  with  a  metal  jacket 
furnished  by  the  boiler  manufacturer.  Self-contained  steel  firebox  boilers 
usually  are  insulated  with  blocks,  cement  and  canvas,  or  rock  wool 
blankets;  HRT  boilers  are  brick  set  and  do  not  require  insulation  beyond 
that  provided  in  the  setting.  It  is  essential  that  the  insulation  on  a  boiler 

261 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

and  adjacent  piping  be  of  non-combustible  material  as  even  slow-burning 
insulation  constitutes  a  dangerous  fire  hazard  in  case  of  low  water  in 
the  boiler. 

PROBLEMS  IN  PRACTICE 

1  •  What  basic  requirements  of  boiler  design  are  to  be  accomplished  with  a 
combination,  boiler  and  oil  burner  unit? 

Combination  units  vary  widely  but  in  general,  the  basic  requirements  of  design  depends 
upon  a  combustion  chamber  of  proper  design  and  arranged  for  the  flame  shape  with 
adequate  heating  surface  for  the  complete  combustion  of  the  fuel. 

2  •  What  is  the  normal  rating  range  of  each  type  of  boiler? 

a.  Cast-iron  boilers  are  rated  at  from  200  to  18,000  sq  ft  EDR. 

b.  Steel  boilers  are  rated  at  from  300  to  50,000  sq  ft  EDR. 

3  •  What  factors  contribute  to  economical  fuel  operation  in  low  pressure 
boilers  burning  coal  or  oil? 

a.  Proper  furnace  volume  for  complete  combustion. 

b.  Arrangement  of  heating  surfaces  in  series  to  create  a  turbulent  and  scrubbing  contact 
of  gases  against  the  convective  surfaces. 

c.  Rapid  internal  water  circulation  which  will  remove  steam  bubbles  from  the  water 
side  of  heating  surfaces  and  allow  other  steam  bubbles  to  be  formed.     Rapid  disen- 
gagement of  steam  bubbles  increases  the  steam  generating  efficiency  of  each  unit 
area  of  heating  surface,  and  thereby  lowers  flue  gas  temperatures. 

4  •  What  ecpiipment  is  usually  directly  attached  to  a  low  pressure  heating 
boiler? 

For  coal  burning  steam  boilers:  water  column,  water  gage,  tri-cocks,  steam  gage,  lever 

pop  safety  valve,  boiler  damper  regulator. 

For  coal  burning  hot  water  boilers:  damper  regulator,  altitude  gage,  thermometer,  relief 

valve. 

For  oil  burning  boilers,  the  damper  regulators  are  omitted  and  the  following  additional 

equipment  is  usually  attached:  automatic  water  feeder,  low  water  cutout,  a  pressure 

control,  and  a  water  temperature  control.   These  are  generally  furnished  by  the  oil 

burner  manufacturer  and  do  not  come  with  the  boiler. 

5  •  What  general  precautions  regarding  the  boiler  should  be  taken  to  make 
sure  a  proposed  beating  installation  will  work  properly? 

a.  Select  the  right  size  and  type  of  boiler. 

&.  Be  sure  the  combustion  space  is  proper  for  the  type  of  fuel  burned. 

c.  Allow  sufficient  space  around  the  boiler  for  cleaning. 

d.  Secure  proper  height  and  area  of  chimney  and  connecting  breeching. 

e.  Clean  the  boiler  thoroughly  and  provide  surface  blowoff  connections  and  bottom 
blowoff  connections  for  periodic  cleaning  after  operation  is  begun. 

/.  See  that  the  boiler  heating  surface  is  cleaned  at  regular  periods. 

g.  Check  flue  gas  temperatures  and  make  a  flue  gas  analysis  at  least  once  a  month. 

h.  Secure  information  and  advice  from  boiler  manufacturer. 

5  •  What  is  the  average  heat  transmission  rate  hi  heating  boilers  hi  Btu  per 
sq  ft  of  beating  surface  per  hour? 

3500  for  coal  burning  boilers;  4200  for  oil  burning  boilers. 


262 


Chapter  14 

RADIATORS  AND  GRAVITY  CONVECTORS 

Heat  Emission  of  Radiators  and  Convectors,  Types  o£  Radi- 
ators, Output  of  Radiators,  Heating  Effect,  Heating  Up  the 
Radiator   and   Convector,    Enclosed    Radiators,    Convectors, 
Selection,  Code  Tests,  Gravity-Indirect  Heating  Systems 

THE  accepted  terms  for  heating  units  are:  (1)  radiators,  for  direct 
surface  heating  units,  either  exposed,  enclosed,  or  shielded,  which 
emit  a  large  percentage  of  their  heat  by  radiation;  and  (2)  connectors,  for 
heating  units  haying  a  large  percentage  of  extended  fin  surface  and  which 
emit  heat  principally  by  convection.  Convectors  are  dependent  upon 
enclosures  to  provide  the  circulation  by  gravity  of  large  volumes  of  air. 

HEAT  EMISSION  OF  RADIATORS  AND  CONVECTORS 

All  heating  units  emit  heat  by  radiation  and  convection.  The  resultant 
heat  from  these  processes  depends  upon  whether  or  not  the  heating  unit  is 
exposed  or  enclosed  and  upon  the  contour  and  surface  characteristics  of 
the  material  in  the  units. 

An  exposed  radiator  emits  less  than  half  of  its  heat  by  radiation,  the 
amount  depending  upon  the  size  and  number  of  sections.  When  the 
radiator  is  enclosed  or  shielded,  radiation  is  further  reduced.  The  balance 
of  the  emission  is  by  conduction  to  the  air  in  contact  with  the  heating 
surface,  and  the  resulting  circulation  of  the  air  warms  by  convection. 

A  convector  emits  practically  all  of  its  heat  by  conduction  to  the  air 
surrounding  it  and  this  heated  air  is  in  turn  transmitted  by  convection  to 
the  rooms  or  spaces  to  be  wanned,  the  heat  emitted  by  radiation  being 
negligible. 

TYPES  OF  RADIATORS 

Present  day  radiators  may  be  classified  as  tubular,  wall,  or  window 
types,  and  are  generally  made  of  cast  iron.  Catalogs  showing  the  many 
designs  and  patterns  available  now  include  a  junior  size  which  is  more 
compact  than  the  standard  unit. 

Pipe  Coils 

Pipe  coils  are  assemblies  of  standard  pipe  or  tubing  (1  in.  to  2  in.)  which 
are  used  as  radiators.  In  older  practice  these  coils  were  commonly  used 
in  factory  buildings,  but  now  wall  type  radiators  are  most  frequently  used 
for  this  service.  When  coils  are  used,  the  miter  type  assembly  is  to  be 

263 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

preferred  as  it  best  cares  for  expansion  in  the  pipe.    Cast  manifolds  or 
headers,  known  as  branch  tees,  are  available  for  this  construction. 

OUTPUT  OF  RADIATORS 

The  output  of  a  radiator  can  be  measured  only  by  the  heat  it  emits. 
The  old  standard  of  comparison  used  to  be  square  feet  of  actual  surface, 
but  since  the  advance  in  radiator  design  and  proportions,  the  surface  area 
alone  is  not  a  true  index  of  output.  (The  engineering  unit  of  output  is  the 
Mb  or  1000  Btu.)  However,  during  the  period  of  transition  from  the  old 
to  the  new,  radiators  may  be  referred  to  in  terms  of  equivalent  square  feet. 
For  steam  service  this  is  based  on  an  emission  of  240  Btu  per  hour  per 
square  foot. 

TABLE  1.   VARIATION  IN  DIMENSIONS  AND  CATALOG  RATINGS  OF 
10-SECTiON  TUBULAR  RADIATORS 


No_«rfTuh«« 

3 

4 

5 

6 

7 

Wiritfl  of  T^'ftt™-                                            Tnp.hea 

4.6-5.1 

6.0-7.0 

8.0-8.9 

9.1-10.4 

11.4-12  8 

L$pgt)i  p^f  Sftfltirm                           ^it            Inches 

2.5 

2.5 

2.5 

2.5 

2.5-30 

HEIGHT  WITH  LEGS—  INCHES 

HEJ 

LT  EMISSION— 

EQUIVALENT  S 

QUA.RE  FEET 

13-14 

20 

25  0-32  5 

16-18 

28.5 

30  0-38  3 

20-21 
22-23 
25-26 
30-32 
36-38 

15.0-17.5 
20.0-21.3 
20.0-26.7 
25.0-30.9 
30.0-36.7 

20.0-22.5 
25 
25.0-27.5 
33.3-35.0 
40.0-42.5 

25.0-31.2 
30.0-33.9 
32.5-39.8 
40.0-48.6 
50.0-56.5 

30 
35 
37.5-40.0 
50 
60 

36.7-45.0 
40.0-45.2 
50.0-53.5 
63.3-62.5 
70.0-75.4 

Output  of  Tubular  Radiators 

^  Table  1  illustrates  the  difficulty  in  tabulating  tubular  radiator  outputs 
since  there  is  so  much  variation  in  design  between  the  products  of  the 
different  manufacturers.  Only  on  the  four-tube  and  six-tube  sizes  is  there 
any  practical  agreement  in  output  value.  The  heat  emission  values 
appear  as  square  feet  but  are  entirely  empirical,  being  based  on  the  heat 
emission  of  the  radiator  and  not  on  the  measured  surface. 

Output  of  Wall  Radiators 

An^average  value  of  300  Btu  per  actual  square  foot  of  surface  area  per 
hour  has  been  found  for  wall  radiators  one  section  high  placed  with  their 
bars  vertical.  Several  recent  tests1  show  that  this  value  will  be  reduced 
from  5  to  10  per  cent  if  the  radiator  is  placed  near  the  ceiling  with  the  bars 
horizontal  and  in  an  air  temperature  exceeding  70  F.  When  radiators 
are  placed  near  the  ceiling,  there  is  usually  so  noticeable  a  difference  in 
temperature  between  the  floor  level  and  the  ceiling  that  it  becomes  dif- 
ficult to  heat  the  living  zone  of  a  room  satisfactorily. 


^University  of  Illinois,  Engineering  Experiment  Station  Bulletin  No.  223,  p.  30. 

264 


CHAPTER  14.   RADIATORS  AND  GRAVITY  CONVECTORS 


Output  of  Pipe  Coils 

The  heat  emission  of  pipe  coils  placed  vertically  on  a  wall  with  the 
pipes  horizontal  is  given  in  Table  2.  This  has  been  developed  from  avail- 
able data  and  does  not  represent  definite  results  of  tests.  For  such  coils 
the  heat  emission  varies  as  the  height  of  the  coil.  The  heat  emission  of 
each  pipe  of  ceiling  coils,  placed  horizontally,  is  about  12G  Btu,  156  Btu, 
and  175  Btu  per  linear  foot  of  pipe,  respectively,  for  l-in.t  lj^-in.,  and 
13/2-in.  coils. 

TABLE  2.    HEAT  EMISSION  OF  PIPE  COILS  PLACED  VERTICALLY  ON  A  WALL  (PIPES 
HORIZONTAL)  CONTAINING  STEAM  AT  215  F  AND  SURROUNDED  WITH  AIR  AT  70  F 

Btu  per  linear  foot  of  coil  per  hour  (not  linear  feet  of  pipe) 


SIZE  OF  PIPE 


I 


It?. 


\\i  IN. 


VA  IN. 


Single  row   

132 

162 

185 

±L    s           

Two 

252 

312 

348 

Four   „  _  

440 

545 

616 

Six.  
Eight.  -  

567 
651 

702 
796 

793 
907 

Ten  -  
Twelve  

732 
812 

907 
1005 

1020 
1135 

Effect  of  Paint 

The  prime  coat  of  paint  on  a  radiator  has  little  effect  on  the  heat  output, 
but  the  finishing  coat  of  paint  does  influence  the  radiation  emission.  Since 
this  is  a  surface  effect,  there  is  no  noticeable  change  in  the  convection  loss. 
Thus,  the  larger  the  proportion  of  direct  radiating  surface,  the  greater 
will  be  the  effect  of  painting  on  the  radiation.  Available  tests  are  on  old- 
style  column  type  radiators  which  gave  results  shown  in  Table  3. 

TABLE  3.    EFFECT  OF  PAINTING  32-iN.  THREE  COLUMN,  SIX-SECTION 
CAST-IRON  RADiATORa 


RADIATOR 
No. 

FINISH 

AREA 
SQFT 

COEFFICIENT 
or  HEAT  TRANS. 
BTU 

RELATIVE 
HEATING  VALUE 
PER  CENT 

1 
2 
3 
4 

Bare  iron,  foundry  finish  
One  coat  of  aluminum  bronze...  
Gray  paint  dipped  

27 
27 
27 
27 

1.77 
1.60 
1.78 
1.76 

100.5 
90.8 
101.1 
100.0 

One  coat  dull  black  Pecora  paint  — 

^Comparative  Tests  of  Radiator  Finishes,  by  \V.  H.  Severns  (A.S.H.V.E.  TRANSACTIONS,  Vol.  33, 
1927,  p.  41). 

Effect  of  Superheated  Steam 

Available  research  data  indicate  that  there  is  probably  a  decrease  in 
heat  transfer  rate  for  a  radiator  or  gravity  convector  with  superheated 
steam  in  comparison  with  saturated  steam  at  the  same  temperature. 
The  decrease  is  probably  small  for  low  temperatures  of  superheats  and 
additional  tests  are  necessary  with  varying  degrees  of  superheat  to 
establish  accurate  comparisons  for  all  types  of  radiators  and  convectors2. 

sTests  of  Radiators  with  Superheated  Steam,  by  R.  C.  Carpenter  (A.S.H.V.E.  TRANSACTIONS,  Vol.  7, 
1901,  p.  206). 

265 


HEATING   VENTILATING   AIR  CONDITIONING  GUIDE  1938 


HEATING  EFFECT 

For  several  years  the  heating  effect  of  radiators  has  been  considered  by 
engineers  in  order  to  use  it  for  the  rating  of  radiators  and  in  the  design  of 
heating  systems.  Heating  effect  is  the  useful  output  of  a  radiator,  in  the 
comfort  zone  of  a  room,  as  related  to  the  total  input  of  the  radiator3. 


^CoW  room  temp  m  deg  F 


01234... 
Net  Ib  of  steam  condensed  per  hour 


5  52  Ib  Test  R-E2,  5-tube  rad 
5  62  Ib  Test  R-E61, 3-tube  rad 
5.42  Ib  Test  R-E10, 1-tube  panel  rad 

—  5.50  Ib  Test  R-2c,  (Bui  223)  wall  rad 

5678 


2       3 


HEIGHT  ABOVE  FLOOR  IN  FEET 

FIG.  1.    ROOM  TEMPERATURE  GRADIENTS  AND  STEAM  CONDENSING  RATES  FOR  FOUR 
TYPES  OF  CAST-IRON  RADIATORS  WITH  A  COMMON  TEMPERATURE  AT  THE  60-lN.  LEVEL 

Note  that  the  steam  condensations  are  practically  the  same  for  all  four  radiators  when  the  same  air 
temperature  of  69  F  is  maintained  at  the  60-in.  level.  avr 


6.68  Ib  Test  R-E56, 5-tube  rad. 
6.48  Ib  Test  R-E20, 3-tube  rad. 
6 12  Ib  Test  R-E58, 1-tube  panel  rad. 
55.0  Ib  Test  R-2c,  (Bui.  223}  wall  rad 
7     8 


HEIGHT  ABOVE  FLOOR  IN  FEET 

FIG.  2.    ROOM  TEMPERATURE  GRADIENTS  AND  STEAM  CONDENSING  RATES  FOR  FOUR 
TYPES  OF  CAST-IRON  RADIATORS  WITH  A  COMMON  TEMPERATURE  AT  THE  30-lN  LEVEL 

68  plsma^ai^d  ^  SoSn^fel™  *"  dftoBlt  ^  aU  *™  radiatOre  when  the  sam<  **  *»*«<**•  of 

The  results  of  tests  conducted  at  the  University  of  Illinois  are  shown  in 
*igs.  1  and  24.  For  the  four  types  of  radiators  shown,  the  following;  con- 
clusions are  given: 


«  c   °a»».  by  Dr-  Charles  Brabbee  (A.S.H.V.E.  TRANSACTIONS  Vol  33   1927 


266 


CHAPTER  14.    RADIATORS  AND  GRAVITY  CONVECTORS 


1.  The  heating  effect  of  a  radiator  cannot  be  judged  solely  by  the  amount  of  steam 
condensed  within  the  radiator. 

2.  Smaller  floor-to-ceiling  temperature  differentials  can  be  maintained  with  long,  low, 
thin,  direct  radiators,  than  is  possible  with  high,  direct  radiators. 

3.  The  larger  portion  of  the  floor-to-ceiling  temperature  differential  in  a  room  of 
average  ceiling  height  heated  with  direct  radiators  occurs  between  the  floor  and  the 
breathing  level. 

4.  The  comfort  level  (approximately  2  ft-6  in.  above  floor)  is  below  the  breathing  line 
level  (approximately  5  ft-0  in.  above  floor),  and  temperatures  taken  at  the  breathing 
line  may  not  be  indicative  of  the  actual  heating  effect  of  a  radiator  in  the  room.    The 
comfort-indicating  temperature  should  be  taken  below  the  breathing  line  level. 

5.  High  column  radiators  placed  at  the  sides  of  window  openings  do  not  produce  as 
comfortable  heating  effects  as   long,   low,   direct  radiators  placed  beneath  window 
openings5. 

HEATING   UP   THE  RADIATOR   AND   CONVECTOR 

The  maximum  condensation  occurs  in  a  heating  unit  when  the  steam 
is  first  turned  on6.  Fig.  3  shows  a  typical  curve  for  the  condensation  rate 
in  pounds  per  hour  for  the  time  elapsing  after  steam  is  turned  into  a  cast- 
iron  radiator.  The  data  are  from  tests  on  old  style  column  type  radiators. 


;±    i  u 

85 

Qu 

t  0.8 

« 

oe. 

UJ 

**  OC 

1 

\ 

/ 

\ 

i 

/ 

\ 

V 

\ 

z 

0 
5n, 

/ 

\l 

/ 

\ 

RATE  OF  CONDENSE 

o  c 

K)  4 

/ 

\ 

\ 

/' 

f 

^v 

/ 

10  20  30 

TIME  ELAPSED  AFTER  STEAM  TURNED  INTO  RADIATOR,  MINUTES 


40 


FIG.  3.    CHART  SHOWING  THE  STEAM  DEMAND  RATE  FOR  HEATING  UP  A  CAST-IRON 
RADIATOR  WITH  FREE  AIR  VENTING  AND  AMPLE  STEAM  SUPPLY 

In  practice  the  rate  of  steam  supply  to  the  heating  unit  while  heating  up 
is  frequently  retarded  by  controlled  elimination  of  air  through  air  valves 
or  traps.  Automatic  control  valves  may  also  retard  the  supply  of  steam. 

ENCLOSED  RADIATORS 

The  general  effect  of  an  enclosure  placed  about  a  direct  radiator  is  to 
restrict  the  air  flow,  diminish  the  radiation  and,  when  properly  designed, 
improve  the  heating  effect.  Recent  investigations7  indicate  that  in  the 
design  of  the  enclosure  three  things  should  be  considered: 

'Effect  of  Two  Types  of  Cast-iron  Steam  Radiators  in  Room  Heating,  by  A.  C.  Willard  and  M.  K. 
Fahnestock  (.Heating,  Piping  and  Air  Conditioning,  March,  1930,  p.  185). 

*The  Cooling  and  Heating  Rates  of  a  Room  with  Different  Types  of  Steam  Radiators  and  Convectors, 
by  A.  P.  Kratz,  M.  K.  Fahnestock  and  E.  L.  Broderick  (A.S.H.V.E.  JOURNAL  SECTION,  Heating,  Piping 
and  Air  Conditioning,  April,  1937,  p.  251). 

'University  of  Illinois,  Engineering  Experiment  Station  Bulletin  Nos.  192  and  223,  and  Investigation  of 
Heating  Rooms  with  Direct  Steam  Radiators  Equipped  with  Enclosures  and  Shields,  by  A.  C.  Willard, 
A.  P.  Kratz,  M.  K.  Fahnestock  and  S.  Konzo  (A.S.H.V.E.  TRANSACTIONS,  Vol.  35,  1929,  p.  77). 

267 


HEATING   VENTIIIATING   AIR  CONDITIONING   GUIDE  1938 


1.  There  should  be  better  distribution  of  the  heat  below  the  breathing  line  level  to 
produce  greater  heating  comfort  and  lowered  ceiling  temperatures. 

2.  The  lessened  steam  consumption  may  not  materially  change  the  radiator  heating 
performance. 

3.  The  enclosed  radiator  may  inadequately  heat  the  space. 

A  comparison  between  a  bare  or  exposed  radiator  (A)  and  the  same 
radiator  with  a  well-designed  enclosure  (j5),  with  a  poorly-designed 
enclosure  (C),  and  with  a  cloth  cover  (D)  will  illustrate  the  relative 
heating  effects.  In  Fig.  4  the  curve  (B)  reveals  that  the  enclosed  radiator 
used  less  steam  than  the  exposed  radiator,  but  gave  a  satisfactory  heating 
performance.  A  well-designed  shield  placed  over  a  radiator  gives  about 
the  same  heating  effect.  Curve  (C)  shows  the  unsatisfactory  effects 
produced  by  improperly  designed  enclosures.  Curve  (D)  shows  that  the 


TEMPERATURE  IN  DEG  FAHR 
S  S  3  S 

^^ 

A-, 
^ 

^j 

_—  — 

'^ 

8 

is' 

^ 

^'' 

^ 

? 

3t 

•&' 
^ 

< 

^ 

XX 

>- 

Radiator 

Steam  consumption 

Lb  per  hr 

Per  cent 

V 

/ 

A 
B 
C 
D 

5.44 
4.71 
4.50 
4.59 

100 
86.6 
82.7 
84.4 

2468 
HEIGHT  ABOVE  FLOOR  fN  FEET 


10 
FIG.  4.  STEAM  CONSUMPTION  OF  EXPOSED  AND  CONCEALED  RADIATORS 


effect  of  a  cloth  cover  extending  downward  6  in.  from  the  top  of  the 
radiator  was  to  make  the  performance  unsatisfactory  and  inadequate. 
Practically  all  commercial  enclosures  and  shields  for  use  on  direct 
radiators  are  equipped  with  water  pans  for  the  purpose  of  adding  moisture 
to  the  air  in  the  room.  Tests8  show  that  an  average  evaporative  rate  of 
about  0.235  Ib  per  square  foot  of  water  surface  per  hour  may  be  obtained 
from  such  pans,  when  the  radiator  is  steam  hot  and  the  relative  humidity 
in  the  room  is  between  25  and  40  per  cent.  This  source  of  supply  of 
moisture  alone  is  not  adequate  to  maintain  a  relative  humidity  above 
25  per  cent  on  a  zero  day. 

CONVECTORS  OR  CONCEALED  HEATERS 

Although  any  standard  radiator  may  be  concealed  in  a  cabinet  or 
other  enclosure  so  that  the  greater  percentage  of  heat  is  conveyed  to  the 

•University  of  Illinois,  Engineering  Experiment  Station  Bulletin  No.  230,  p.  20. 

268 


CHAPTER  14.   RADIATORS  AND  GRAVITY  CONVECTORS 


room  by  convection  thereby  resulting  in  a  form  of  gravity  con  vector, 
generally  better  results  are  obtained  with  specially  designed  units  which 
permit  a  free  circulation  of  a  larger  volume  of  air  at  moderate  tempera- 
tures. Since  air  stratifies  according  to  temperature,  moderate  delivery 
temperatures  at  the  outlet  of  the  enclosure  reduce  the  temperature  dif- 
ferential between  the  floor  and  ceiling  and  accordingly  accomplish  the 
desired  heating  effect  in  the  living  zone. 

Fig.  5  shows  a  typical  built-in  convectpr.     The  heating  element  con- 
sisting of  a  large  percentage  of  fin  surface  is  usually  shallow  in  depth  and 


SECTION 
FIG.  5.    TYPICAL  CONCEALED  CONVECTOR  USING  SPECIALLY  DESIGNED  HEATING  UNIT 

placed  low  in  the  enclosure  in  order  to  produce  maximum  chimney  effect 
in  the  enclosure.  The  air  enters  the  enclosure  near  the  floor  line  just 
below  the  heating  element,  is  moderately  heated  in  passing  through  the 
core  and  delivered  to  the  room  through  an  opening  near  the  top  of  en- 
closure. Since  the  air  can  only  enter  the  enclosure  at  the  floor  line,  the 
cooler  air  in  the  room  which  always  lies  at  this  level,  is  constantly  being 
withdrawn  and  replaced  by  the  warmer  air.  This  air  movement  accom- 
plishes the  desired  reduction  in  temperature  differentials  and  assures 
maximum  comfort  in  the  living  zone. 

The  Convector  Manufacturers  Association  has  adopted  the  A.S.H.V.E. 
Standard9  in  the  formulation  of  its  ratings  and  has  compiled  a  tentative 


•A.S.H.V.E.  Standard  Code  for  Testing  and  Rating  Concealed  Gravity  Type  Radiation  (Steam), 
(A.S.H.V.E.  TRANSACTIONS,  Vol.  37.  1931.  p.  367);  (Hot  Water).  (A.S.H.V.E.  TRANSACTIONS,  Vol.  3<), 
1933,  p.  237). 

269 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

standard  of  heating  effect  allowances  for  various  enclosure  heights  to  be 
included  in  the  ratings  by  its  members. 

All  published  ratings  bearing  the  title  C.M.C.  Ratings  (Convector  Manu- 
facturers Certified  Ratings)  indicate  that  the  convectors  have  been  tested 
in  accordance  with  the  A.S.H.V.E.  Code  by  an  impartial  and  disinterested 
laboratory  and  that  the  ratings  have  been  approved  by  the  Standardiza- 
tion Committee  of  the  Convector  Manufacturers  Association. 

Concealed  heaters  or  cpnvectors  are  generally  sold  as  completely 
built-in  units.  The  enclosing  cabinet  should  be  designed  with  suitable 
air  inlet  and  outlet  grilles  to  give  the  heating  element  its  best  performance. 
Tables  of  capacities  are  catalogued  for  various  lengths,  depths  and  heights, 
and  combinations  are  available  in  several  styles  for  installations,  such  as 
the  wall-hung  type,  free-standing  floor  type,  recess  type  set  flush  with  wall 
or  offset,  and  the  completely  concealed  type.  Most  of  these  types  may  be 
arranged  with  a  top  outlet  grille  in  a  plane  parallel  with  the  floor,  although 
the  front  outlet  is  practically  standard.  In  cases  where  enclosures  are  to 
be  used  but  are  not  furnished  by  the  heater  manufacturer,  it  is  important 
that  the  proportions  of  the  cabinet  and  the  grilles  be  so  designed  that  they 
will  not  impair  the  performance  of  the  assembled  convector.  It  is  impor- 
tant that  the  enclosure  or  housing  for  the  convector  fit  as  snugly  as  pos- 
sible so  that  the  air  to  be  heated  must  pass  through  the  convector  and 
cannot  be  by-passed  in  the  enclosure. 

The  output  of  a  convector,  for  any  given  length  and  depth,  is  a  variable 
of  the  height.  Published  ratings  are  generally  given  in  terms  of  equiva- 
lent square  feet,  corrected  for  heating  effect.  However,  an  extended 
surface  heating  unit  is  entirely  different  structurally  and  physically  from 
a  direct  radiator  and,  since  it  has  no  area  measurement  corresponding  to 
the  heating  surface  of  a  radiator,  many  engineers  believe  that  the  per- 
formance of  convectors  should  be  stated  in  Btu's.  For  steam  convectors, 
as  for  radiators,  240  Btu  per  hour  may  be  taken  as  an  equivalent  square 
foot  of  radiation. 

RADIATOR  AND  CONVECTOH  SELECTION 

Since  the  capacity  of  a  radiator  varies  as  the  1.3  power  and  a  convector10 
as  the  1.5  power  of  the  temperature  difference  between  the  inside  of 
radiator  and  surrounding  air  it  is  obvious  that  for  other  than  70  F  room 
temperatures  the  heat  emission  will  be  other  than  240  Btu  per  square  foot 
of  rating.  Therefore  in  selecting  the  size  of  radiator  or  convector  to  be 
used  it  is  necessary  to  correct  for  this  difference.  Table  4  shows  factors  by 
which  radiation  requirements,  as  determined  by  dividing  heat  load  by 
240,  shall  be  multiplied  to  obtain  proper  radiator  or  convector  sizes  from 
published  rating  tables  for  room  temperatures  ranging  between  50  and 
80  F  as  well  as  for  steam  or  water  temperatures  from  150  to  300  F.  For 
other  room  and  heating  medium  temperatures  the  factor  is  determined  by 
the  following  formulae: 

For  radiators: 

Cs  -  /215  ~  70V'3 


"Factors  Affecting  the  Heat  Output  of  Convectors,  by  A.  P.  Kratz,  M.  K.  Fahnestock,  and  E.  L.  Brod- 
erick  (A.S.H.V.E.  TRANSACTIONS,  Vol.  40,  1934,  p.  443). 

270 


CHAPTER  14.   RADIATORS  AND  GRAVITY  CONVECTORS 


For  con  vectors: 


where 


Cs  =  correction  factor. 
/a  —  steam  temperature,  degrees  Fahrenheit. 
tT  —  room  temperature,  degrees  Fahrenheit, 
/i  =  average  inlet  air  temperature,  degrees  Fahrenheit. 

TABLE  4.    CORRECTION  FACTORS  FOR  DIRECT  CAST-IRON  RADIATORS  AN*I> 
Cox  VECTOR  HEATERS* 


STEAM               .,                           FACTORS  FOR  DIRECT                               „ 
PRESS.             ,  bTEAM                   CAST-IRON  RADIATOR                              FACTORS  FOR  (  UVVLIT  JKS 

AFFHOi.                 .   YVxTEH  '                         R           *P                              P                         '                   T  ,.          4  .  !  T^..^^^..^.  -^«  t' 

fiagp      '      Ahh.         TEMP. 

Vacuum       Lb  p<-r   '       F                         ' 

In.  Hg     !     Sqlri.    j 

80   ,    75        70       65 

60 

55    ,    50       80       75 

70    ,    65       GO 

J3 

5U 

22A      ,        3.7      |      150 

2.58    2.36  ,  2.17     2.00 

1.86 

1.73  ]  1.62  ;  3.11    2.83 

2.57    2.35 

2.15 

1.98 

1.8* 

20.3              4.7      !      160 

2.17 

2.00  |  1.86 

1.73 

1.62 

1.52     1.44  I!  2.57 

2.35 

2.15     1.98 

1.84 

1.71 

1.59 

17.7       ,       6.0      j      170 

1.86 

1.73 

1.62 

1.52 

1.44 

L35  i  1.28  ;{  2.15 

1.98 

1.84  i  1.71 

1.59 

1.49 

1.40 

14.6              7.5      .      180 

1.62  '  1.52     1.44 

1.35 

1.28 

1.21     1.15  |  1.84 

1.71 

1.59  i  1.49 

1.40 

1.32 

1.24 

10.9              9.3      !      190 

1.44     1.35  ,  1.28 

1.21 

1.15 

1.10 

1.05  i.  1.59 

1.49 

1.40  i  1.32 

1.24 

117 

1.11 

6.5       !      11.5      |      200 

1.28 

1.21 

1.15  ;  1.10 

1.05 

1.00 

0.96  i  1.40 

1.32 

1.24  ;  1.17 

1.11 

1.05 

1.00 

LbperSqln.'                I 

•           :i 

! 

1          •      15.6      i      215        1.10  !  1.05  i  1  00 

0.96 

0.92  '  0.88 

O.S5  I-  1.17     1.11 

1.05  i  1.00 

095 

0.91 

087 

6          '21         1      230     !  0.96 

0.92 

0.88 

0.85 

0.81    0.78 

0.76  j  1.00    0.95 

0.91  |  0.87 

0.83 

0.79 

0.76 

15         ,      30              250     j  0.81 

0.78 

0.76    0.73 

0.70 

0.68 

0.66  'I  0.83 

0.79 

0.76  ,  0.73  ;  0  70 

0.68 

005 

27         :      42        i      270       0  70 

068 

0.66    0.64 

0.62 

0.60 

0.58  ;|  0.70 

0.68 

0.65  I  0.63  j  0.60 

0.58 

0.56 

52         i      67        !     300     1  0.58 

0.57 

0.55 

0.53 

0.52 

0.51 

0.49:i  0.56    0.54 

0.53  i  0.51  !  0.49  j  0.4* 

0.47 

»To  determine  the  heater  size  for  a  given  space,  divide  the  heat  loss  in  Btu  per  hour  by  240  and  multiply 
the  result  by  the  proper  factor  from  the  above  table. 

To  determine  the  heating  capacity  of  a  heater  at  other  than  standard  conditions,  divide  the  heating 
capacity  at  standard  conditions  by  the  proper  factor  from  the  above  table. 

CODE  TEST  FOR  RADIATORS  AND  CONVECTORS 

As  previously  indicated,  the  output  of  radiators  and  convectors  is  still 
designated  by  the  terms  of  older  practice,  but  this  is  gradually  giving  place 
to  an  engineering  method  of  designating  heat  emission.  The  A.S.H.V.E. 
has  adopted  the  following  standards :  Code  for  Testing  Radiators  (1927) ; 
Codes  for  Testing  and  Rating  Concealed  Gravity  Type  Radiation  (Steam, 
1932,  and  Hot  Water,  1933). 

For  steam  services  the  actual  condensation  weight  is  taken  without  any 
allowance  for  heating  effect ;  for  hot  water  services  the  weight  of  circulated 
water  is  used  without  allowance  for  heating  effect*  In  all  cases  the  total 
heat  transmission  varies  as  the  1.3  power  for  radiators11  and  the  1.5 
power  for  convectors12  of  the  temperature  difference  between  that  inside 
the  radiator  and  the  air  in  the  room,  and  is  expressed  in  Btu  or  Mb 
per  hour. 

Standard  test  conditions  specify  either  a  steam  pressure  of  1  Ib  gage 
(215  F),  or  hot  water  at  170  F  and  a  room  temperature  of  70  F  for  radi- 
ators, or  an  inlet  air  temperature  of  65  F  for  convectors.  The  heating 
capacity  of  a  steam  radiator  or  steam  converter  is  determined  as  follows: 

f/t  =  WJitt  W 


"Loc.  Cit.  Note  9. 

»Loc.  Cit.  Notes  9  and  10. 


271 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

where 

Ht  =  Btu  per  hour  under  test  conditions. 
Ws  ~  condensation  in  pounds  per  hour, 
//fg  =  latent  heat  in  Btu  per  pound. 

Ht  may  be  converted  to  standard  conditions  of  code  ratings  by  using 
the  proper  correction  factor  from  the  following  formulae : 
For  radiators: 

r  -  (21*  -  70V-3  -  (  — 1M__V'3  t*\ 

L*   ~   \Ta-TrJ        ~   \TS  -  TT  )  W 

For  con  vectors: 

Cs  .    (™=£)"  =  (T^)"  0) 

The  output  under  standard  conditions  will  be: 

Ha  *  Cs  Ht  W 

where 

Cs  =  correction  factor. 

rs  =  steam  temperature  during  test,  degrees  Fahrenheit. 

TT  =  room  temperature  during  test,  degrees  Fahrenheit. 

T{  =  inlet  air  temperature  during  test,  degrees  Fahrenheit. 

Hs  =  heat  emission  rating  under  standard  conditions,  Btu  per  hour. 

Similarly,  for  hot  water  converters,  the  output  under  test  conditions  may 
be  determined  as  follows: 


H  =  w  (B!  -  02)  ^p  (5) 

where 

H  =  Btu  per  hour  under  test  conditions. 
W  =  pounds  of  water  handled  during  test. 

81  —  average  temperature  of  inlet  water,  degrees  Fahrenheit. 

82  =  average  temperature  of  outlet  water,  degrees  Fahrenheit. 
t  -  duration  of  test,  seconds. 

To  convert  test  results  to  standard  conditions,  the  following  correction 
factor  is  used: 

170-65      \i-«        /  105 

(6) 


•*  1 


It  has  been  shown  that  when  the  exponent  1.5  is  used  the  range  of  error 
is  less  than  3  per  cent13  for  convectors. 

GRAVITY-INDIRECT   HEATING   SYSTEMS14 

The  heating  units  for  this  system  are  usually  of  the  extended  surface 
type  for  steam  or  hot  water,  and  are  installed  about  as  shown  in  Fig.  6. 
The  temperature  and  volume  of  the  air  leaving  the  register  must  be  great 

1!Loc.  Cit.  Note  10. 

"For  further  information  on  this  subject  see  A.S.H.V.E.  Code  of  Minimum  Requirements  for  the  Heating 
and  Ventilation  of  Buildings  (edition  of  1929)  and  Mechanical  Equipment  of  Buildings,  by  Harding  and 
Willard.  Vol.  1,  second  edition,  1929. 

272 


CHAPTER  14.   RADIATORS  AND  GRAVITY  CONVECTORS 

enough  so  that  in  cooling  to  room  temperature  the  heat  available  will  jus 
equal  the  heat  loss  during  the  same  time.  In  cases  where  ventilation  is  < 
requirement,  the  air  volume  needed  may  become  so  large  that  the  enterini 
air  temperature  will  be  but  slightly  above  the  room  temperature.  T< 
establish  and  maintain  a  constant  heat  flow,  provision  must  be  made  fo 
removing  the  air  in  the  room,  after  it  has  cooled  to  the  desired  room  tern 
perature,  by  a  system  of  vent  flues  or  ducts.  As  the  air  flow  is  maintainec 


Supports'hung  from  joist  or  floor  above 


Felt  Strips 
at  Edge" 


Recircutatmg  Duct- 

FIG.  6.    GRAVITY-INDIRECT  HEATING  SYSTEM* 

•See  Mechanical  Equipment  of  Buildings,  by  Harding  and  Willard,  Vol.  I,  second  edition,  1929. 

by  natural  draft  and  this  gravity  head  is  very  slight,  it  is  necessary  to 
make  all  ducts  as  short  as  possible,  especially  the  runs  from  the  heating 
units  to  the  base  of  the  vertical  warm  air  flues.  Gravity-indirect  arrange- 
ments, such  as  illustrated  in  Fig.  6,  are  not  to  be  generally  recommended 
for  hot  water  systems  unless  the  water  temperature  can  be  maintained  at 
a  reasonably  high  temperature  and  rapid  circulation  of  the  water  can  be 
had. 


PROBLEMS  IN  PRACTICE 

*he  effect  on  the  heat  output  of  a  wall  radiator  when  installed  on 
the  ceiling  of  a  room? 

Because  the  temperature  differential  is  increased  between  the  floor  level  and  the  ceiling 
when  a  wall  radiator  is  placed  near  the  ceiling,  the  heat  output  may  be  decreased  from 
5  to  10  per  cent.  Under  such  circumstances  it  becomes  difficult  to  heat  the  living  zone 
of  a  room  satisfactorily.  s 

273 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

2  •  What  are  the  principal  differences  between  a  radiator  and  a  convector? 

A  radiator  is  commonly  thought  of  as  a  commercial  heating  unit  having  a  maximum 
amount  of  direct  heating  surface,  whereas  a  convector  is  a  heating  device  in  which  the 
extended  or  secondary  surface  may  be  several  times  that  of  the  prime  surface  and  which 
is  specially  designed  to  utilize  to  the  fullest  extent  the  convection  principal  of  heating. 
The  radiator  ordinarily  has  vertical  tubular  chambers  for  the  heating  medium  but  most 
converters  have  horizontal  tubular  chambers  to  which  fins  are  attached  so  as  to  form 
vertical  flues  for  the  passage  of  air.  While  radiators  are  either  exposed,  enclosed,  or 
shielded,  convectors  are  concealed  by  means  of  a  tight-fitting  enclosure.  Radiators  are 
commonly  made  of  cast  iron  but  convectors  may  be  made  of  a  combination  of  metals, 
such  as  copper  and  brass,  or  copper  and  aluminum,  as  well  as  entirely  of  cast  iron. 

3  •  How  did  the  term  heating  effect  come  into  use? 

It  has  been  found  that  a  room  requiring  a  radiator  of  a  certain  determined  capacity 
could  under  certain  conditions  be  properly  heated,  with  less  temperature  gradient  be- 
tween^ floor  and  ceiling  and  with  less  steam  condensation,  by  the  same  radiator  or  by  one 
of  a  different  design  having  the  same  commercially  rated  capacity.  This  resulted  in  the 
use  of  the  term  heating  effect  to  apply  to  the  useful  heat  output  of  a  radiator,  in  the  com- 
fort zone  of  a  room,  as  related  to  the  total  input  to  the  radiator. 

4  •  Is  it  necessary  to  make  any  allowance  for  the  performance  of  a  convector 
because  it  is  enclosed? 

No.  The  commercial  ratings  of  convectors  have  been  determined  by  testing  the  con- 
vectors  in  proper  enclosures  with  grilles  in  place  just  as  they  should  be  installed  for 
ordinary  service. 

5  •  On  what  basis  are  the  capacities  of  convectors  published? 

Published  ratings  of  convectors  are  expressed  in  equivalent  square  feet  of  direct  cast 
iron  radiation.  Some  manufacturers  have  increased  their  ratings  by  as  much  as  30  per 
cent  to  allow  for  a  supposed  improved  heating  effect.  Tests  indicate  that  the  credit  to 
be  given  heating  effect  is,  in  all  cases,  probably  less  than  10  per  cent,  and  in  many  cases 
negligible. 

6  •  How  are  fins  of  convectors  attached  to  the  tubes  or  prime  surface? 

Tubes  or  a  solid  core  may  be  forced  through  piercings  in  the  fins  under  pressure  or  the 
tubes  may  be  expanded  into  the  holes  through  the  fins.  In  addition  a  metallic  bonding 
agent  is  sometimes  used  to  insure  permanent  contact. 

7  •  What  is  the  procedure  in  selecting  a  convector  when  the  required  amount 
of  radiation  is  known? 

First  the  limiting  factor  or  factors  of  the  enclosure  must  be  determined  so  the  available 
size  of  the  wall  recess  can  be  found.  Manufacturers'  catalogs  show  capacities  of  con- 
vectors  of  each  standard  length  and  depth  with  varying  enclosure  heights.  From  these 
capacity  tables,  the  proper  convector  of  the  required  capacity  can  be  selected  for  the 
available  wall  recess.  If  all  three  dimensions  of  the  wall  recess  are  insufficient  to  accom- 
modate a  convector  of  the  required  capacity,  the  available  height  and  length  can  be 
maintained,  but  greater  depth  can  be  obtained  by  using  a  partially  recessed  enclosure. 

8  •  Given  a  room    to  be  heated  to  80  F  with  outside   temperature  at  0  F, 
assume  the  heat  loss  under  these  conditions  to  be  10,000  Btu  per  hour.    Deter- 
mine the  size  of  the  steam  radiator  to  be  installed. 

A  square  foot  of  radiation  is  equivalent  to  a  heat  emission  of  240  Btu  per  hour  under 
Sta2^d  conditions  of  steam  at  one  pound  gage  pressure  (215  F)  and  surrounding  air 
at  70  F.  With  surrounding  air  at  80  F,  the  heat  emission  from  a  radiator  will  be  less. 
Under  these  conditions,  the  heat  emission  will  not  be  240  Btu  per  square  foot  of  catalog 
rating  per  Jiour,  but  240  Cs. 


-  ( 
"  V 


~  ft   V'*  -  /^215  -  SON1-3      n™« 
215  -  70}      ~  V215  -  70  J      "  °'912' 


and  240  C8  -  240  X  0.912  -  218.5  Btu.    Therefore,  the  size  of  the  radiator  to  be 
selected  shall  have  a  catalog  rating  of  10,000  divided  by  218.5  or  45.8  sq  ft. 


274 


Chapter  15 

STEAM  HEATING  SYSTEMS 

Gravity  and  Mechanical  Return,  Gravity  One-Pipe  Air- Vent 
System,  Gravity  Two-Pipe  Air- Vent  System,  One-Pipe  Vapor 
System,  Two-Pipe  Vapor  System,  Atmospheric  System, 
Vacuum  System,  Sub-Atmospheric  System,  Orifice  System, 
Zone  Control,  Auxiliary  Conditioning  Unit,  Condensation 
Return  Pumps,  Vacuum  Pumps,  Traps 

THE  essential  features  of  the  common  type  of  steam  heating  systems 
are  described  in  this  chapter.  They  may  be  classified  according  to  the 
piping  arrangement,  the  accessories  used,  the  method  of  returning  the  con- 
densate  to  the  boiler,  the  method  of  expelling  air  from  the  system,  or  the 
type  of  control  employed.  Information  concerning  the  design  and  layout 
of  steam  heating  systems  will  be  found  in  Chapter  16. 

GRAVITY  AND  MECHANICAL  RETURN 

In  gravity  systems  the  condensate  is  returned  to  the  boiler  by  gravity 
due  to  the  static  head  of  water  in  the  return  mains.  The  elevation  of  the 
boiler  water  line  must  consequently  be  sufficiently  below  the  lowest 
heating  units  and  steam  main  and  dry  return  mains  to  permit  the  return 
of  condensate  by  gravity.  The  water  line  difference1  must  be  sufficient  to 
overcome  the  maximum  pressure  drop  in  the  system  and,  when  radiator 
and  drip  traps  are  used  as  in  two-pipe  vapor  systems,  the  operating 
pressure  of  the  boiler.  The  condensing  return  of  the  radiation  will 
increase  the  required  water  line  difference  and  is  especially  important 
where  the  radiation  is  a  type  having  a  high  condensing  rate.  This  applies 
only  to  closed  circuit  systems,  where  the  condensation  is  returned  to  the 
boiler.  If  the  condensation  is  wasted,  no  water  line  difference  is  required, 
but  other  conditions  are  introduced  which  warrant  the  use  of  an  appro- 
priate mechanical  system  in  preference  to  wasting  the  condensate. 

In  mechanical  systems  the  condensate  flows  to  a  receiver  and  is  then 
forced  into  the  boiler  against  the  boiler  pressure.  The  lowest  parts  of  the 
supply  side  of  the  system  must  be  kept  sufficiently  above  the  water  line 
of  the  receiver  to  insure  adequate  drainage  of  water  from  the  system,  but 
the  relative  elevation  of  the  boiler  water  line  is  unimportant  in  such  cases 


JThe  icatcr  line  difference  is  the  distance  between  the  water  line  of  the  boiler  and  the  level  of  the  water 
in  the  dry  or  wet  return  main.    (See  Fig.  4.) 

275 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


except  that  the  head  on  the  pump  or  trap  discharge  becomes  greater  as 
the  height  of  the  boiler  water  line  above  the  trap  or  pump  increases. 

There  are  three  general  types  of  mechanical  returns  in  common  use, 
namely,  (1)  the  mechanical  return  trap,  (2)  the  condensation  return 
pump,  and  (3)  the  vacuum  return  pump.  Further  information  on  pumps 
and  traps  will  be  presented  later  in  this  chapter. 

GRAVITY  ONEPIPE  AIR-VENT  SYSTEM 

In  the  gravity  one-pipe  air- vent  system  each  radiator  has  but  a  single 
connection  through  which  steam  must  enter  and  condensation  must 
return  in  the  opposite  direction.  Each  radiator  has  an  individual  air 
valve. 

Up-Feed  Gravity  One-Pipe  Air-Vent  System 

This  system  is  the  most  common  of  all  methods  of  steam  heating, 
especially  for  small  size  installations,  due  largely  to  its  low  cost  of  instal- 


Air  valve 


Hartford 
return  — • - 
connection 


Riser  dripped 
Boiler  water  line^ 


Wet  return^ 
FIG.  1.    TYPICAL  UP-FEED  GRAVITY  ONE-PIPE  AIR- VENT  SYSTEM 

lation  and  its  simplicity.  Where  the  size  of  the  system  is  moderate  or 
largest  cannot  be  assumed  that  these  systems  will  be  lower  in  cost  than 
two-pipe  systems  using  steam  traps.  In  some  instances  it  has  been  found 
that  the  cost  of  one-pipe  systems  under  these  conditions  is  greater  owing 
to  the  higher  cost  of  labor  and  materials  due  to  the  larger  pipe  sizes.  As 
will  be  seen  from  Fig.  1,  the  steam  piping  rises  to  a  point  as  high  as  possible 
at  the  boiler  and  pitches  downward  from  this  location  until  the  far  end  of 
the  main  or  mains  is  reached.  At  the  far  ends  drips  are  taken  off  at  the 
low  points  of  the  steam  mains,  are  water-sealed  below  the  boiler  water 
line,  and  then  brought  back  to  the  boiler  in  a  wet  return.  Single  pipe  risers 


276 


CHAPTER  15.   STEAM  HEATING  SYSTEMS 


are  branched  off  the  main  or  mains  to  feed  the  radiators,  the  steam  passing 
up  the  riser  and  the  condensation  flowing  down  it.  The  steam  and  con- 
densation flow  in  opposite  directions  in  the  riser  but  after  the  condensa- 
tion enters  the  steam  main  it  flows  in  the  same  direction  as  the  steam  and 
is  disposed  of  through  the  drip  connection  at  the  end  of  the  main.  In 
buildings  of  several  stories,  it  is  customary  to  drip  the  heel  of  each  riser 
separately,  whereas  in  one-  or  two-story  buildings  this  is  not  necessary. 
Both  types  of  branches  and  risers  are  shown  in  Fig.  1. 

Rapid  elimination  of  air  and  condensation  from  the  steam  piping  is 
essential  to  the  successful  operation  of  this  system.  It  is  therefore 
desirable  that  the  venting  and  dripping  of  the  steam  main  in  long  runs  be 
made  at  several  intermediate  points  where  the  steam  main  may  again  be 
brought  to  a  higher  elevation. 

It  is  desirable  to  install  the  air-vent  valves  on  the  steam  main  about  a 
foot  ahead  of  the  drips,  as  is  indicated  in  Fig.  1  to  prevent  possible  damage 
to  the  mechanism  of  the  air- vent  valve  by  water,  in  case  the  valves  are 
installed  directly  above  the  drips. 

Horizontal  branches  to  radiators  and  risers  should  be  pitched  at  least 
J^  in.  in  10  ft  downward  toward  the  riser  or  vertical  pipe,  and  the  hori- 


Up  to  radiator  or  riser- 
-  Pitch 


Steam  main 

— 5  ft  approximately 


FIG.  2.     TYPICAL  STEAM  RUNOUT  WHERE      FIG.  3.   TYPICAL  STEAM  RUNOUT  WHERE 
RISERS  ARE  NOT  DRIPPED  RISERS  ARE  DRIPPED 

zontal  branches  from  the  steam  main  should  be  graded  at  least  this 
amount  toward  the  main,  except  where  the  heel  of  the  riser  is  dripped,  in 
which  case  the  branch  should  pitch  down  toward  the  riser  drip  (Figs.  2 
and  3).  The  return  line,  if  wet,  may  be  run  without  pitch  or  may  be 
pitched  in  either  direction,  but  if  it  is  necessary  to  carry  the  return  main 
overhead  for  any  distance  before  dropping,  the  return  should  slope  down- 
ward with  the  flow.  It  is  desirable  to  install  the  wet  return  pipe  with  a 
pitch  so  that  the  system  may  be  drained  to  prevent  freezing  in  case  the 
building  remains  unoccupied  for  a  considerable  length  of  time. 

The  radiator  valves  may  be  of  the  angle-globe  or  gate  type.  They 
should  not  be  of  the  straight-globe  type  because  the  damming  effect  of  the 
raised  valve  seat  interferes  with  the  flow  of  condensation  through  the 
valve.  Graduated  valves  cannot  be  used,  as  the  steam  valves  on  this 
system  must  be  fully  open  or  closed  to  prevent  the  radiators  filling  with 
water.  Air  valves  may  be  manual  or  automatic,  with  or  without  a  check 
to  prevent  the  re-entrance  of  expelled  air.  Usually  the  automatic  type  is 
installed.  An  objection  to  one-pipe  steam  systems  is  that  the  heat  is  all 
on  or  all  off,  with  no  intermediate  position  possible.  However,  intelligent 

277 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 

use  of  the  on-and-off  method  of  manual  control  gives  reasonably  satis- 
factory results.  Improved  systems  and  devices  are  now  available  which 
make  it  possible  to  obtain  a  modulating  effect  from  one-pipe  gravitv 
heating  systems.  J 

It  is  important  that  the  lowest  points  of  the  steam  mains  and  heating 
units  be  kept  sufficiently  above  the  water  line  of  the  boiler  to  prevent 


Boiler  steam  pressure 

u-x-ii; 


Steam  pressure  at 
end  of  main 

Return  water 


/Floor 


FIG.  4.    DIFFERENCE  IN  STEAM  PRESSURE 

ON  WATER  IN  BOILER  AND  AT  END 

OF  STEAM  MAIN 


Supply  riser- 


^ 


Supply  main 


^Drop  riser 
Air  valve 


Hartford 

return 

connection 


Mr  valve 


Air  vent 


"Air  valve 


return 


FIG.  5.    TYPICAL  DOWN-FEED  GRAVITY  ONE-PIPE  AIR-  VENT  SYSTEM 

18in-  is  suffident  tat  construction  limitations  foe- 


278 


CHAPTER  15.  STEAM  HEATING  SYSTEMS 


.usually  about  3  in.  unless  the  pipes  are  small  or  full  of  sediment  ,  and  it  will  rise  still 
farther  it  a  check  valve  is  installed  in  the  return  so  as  to  obtain  sufficient  head  to  lift  the 
tongue  of  the  check  (usually  4  in.  will  be  necessary  /. 

If  a  one-pipe  steam  system  is  designed,  for  example,  for  a  total  pressure  drop  of  l/$  Ib, 
and  utilizes  an  Undenmters'  Loop*  instead  of  a  check  valve  on  the  return,  the  rise  in  the 
water  level  at  the  far  end  of  the  return  due  to  the  difference  in  steam  pressure  would  be 
Ys  of  28  in.,  or  3H  in.  Adding  3  in.  to  this  for  the  flow  through  the  return  main  and  6  in. 
as  a  factor  of  safety  gives  12J^  in.  as  the  distance  the  bottom  of  the  lowest  part  of  the 
steam  main  and  all  heating  units  must  be  above  the  boiler  water  line.  The  same  system 
however,  installed  and  sized  for  a  total  pressure  drop  of  J/£  Ib,  and  with  a  check  in  the 
return,  would  require  1A  of  2S  in.,  or  14  in.,  for  the  difference  in  steam  pressure,  3  in.  for 
the  flow  through  the  return,  4  in.  to  operate  the  check,  and  6  in.  for  a  factor  of  safety, 
making  a  total  of  27  in.  as  the  required  distance.  Higher  pressure  drops  would  increase 
the  distance  accordingly. 

Down-Feed  Gravity  One-Pipe  Air-Vent  System 

In  the  overhead  down-feed  gravity  one-pipe  air- vent  system  there  is  no 
change  over  the  up-feed  system  in  the  radiators,  the  radiator  valves,  the 
air  valves,  or  the  radiator  runouts  as  far  back  as  the  risers.  Beyond  this 


Pitch 


Steam  drop  to  radiators  — |  ^  Steam  drop  to  radiators 


FIG.  6.  STEAM  RUNOUTS  DRIPPING  MAIN         FIG.  7.   STEAM  RUNOUTS  WITH  MAIN 

DRIPPED  AT  END  ONLY 

*  point  there  are  basic  differences.  The  steam  is  taken  from  the  boiler  and 
carried  to  the  top  of  the  building  as  near  the  boiler  as  possible  (Fig.  5). 
If  the  run  to  the  main  riser  is  long,  or  if  the  riser  extends  several  stories  in 
order  to  reach  the  top,  the  bottom  of  the  riser  should  be  dripped  into  the 
wet  return.  The  horizontal  main  is  taken  off  the  top  of  the  riser  and 
grades  down  from  the  riser  toward  all  of  the  drops,  each  drop  taking  its 
share  of  the  main  condensation  (Fig.  6),  or  all  of  the  drops  except  the  last 
may  be  taken  from  the  top  of  the  main  (Fig.  7),  the  last  drop  being  from 
the  bottom  and  serving  as  a  drain  for  the  entire  main.  As  the  overhead 
main  does  not  carry  any  condensation  from  the  radiators  it  is  immaterial 
which  method  is  used.  The  air  vent  shown  on  the  main  just  before  the 
last  drop  (Fig.  5)  may  be  placed  at  this  point  or  it  may  be  located  at  the 
bottom  of  the  drop  under  the  last  radiator  connection  and  sufficiently 
above  the  water  line  of  the  boiler  to  prevent  flooding. 

GRAVITY  TWO-PIPE  AIR-VENT  SYSTEM 

The  gravity  two-pipe  system  is  now  considered  obsolete  although  many 
of  these  systems  are  still  in  use  in  older  buildings.  Separate  supply  and 
return  mains  and  connections  are  required  for  each  heating  unit;  air 
valves  are  installed  on  the  heating  units  and  mains;  hand  valves  are 
installed  on  the  returns. 


*See  discussion  of  piping  details  in  Chapter  16. 

279 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


Up-Feed  Gravity  Two-Pipe  System 

This  system  (Fig.  8)  has  a  steam  and  a  return  connection  to  each 
radiator.  The  radiator  valves  for  steam,  return,  and  air  are  the  same  as 
those  described  for  the  gravity  one-pipe  air-vent  system.  The  steam 
main  is  run  and  pitched  in  the  same  manner  as  in  the  one-pipe  system, 
but  the  returns  from  each  radiator  are  connected  into  a  separate  return 
line  system  which  has  its  risers  carried  down  and  joined  to  a  wet  return 
line  under  the  boiler  water  line  level.  Where  the  return  has  to  be  kept 
high  to  function  as  a  dry  return,  it  is  advisable  to  connect  the  return 
risers  to  the  dry  return  main  through  water  seals  about  36  in.  deep,  as 


Air  valve 


Hartford 

return 

connection 


£ Wet  return 


FIG.  8.    TYPICAL  UP-FEED  GRAVITY  Two- PIPE  AIR- VENT  SYSTEM 


shown  in  Fig.  9,  to  prevent  steam  from  one  riser  entering  another  and 
closing  the  air  valves  on  the  nearest  radiators. 

Down-Feed  Gravity  Two-Pipe  System 

The  steam  main  in  the  down-feed  system  is  carried  to  the  top  of  the 
building,  and  the  piping  of  the  steam  side  is  arranged  practically  as  in  the 
down-feed  one-pipe  gravity  system.  The  drips  at  the  bottoms  of  the 
steam  drops  and  the  runouts  to  the  radiators  are  similar  to  those  shown 
in  Fig.  8  for  the  up-feed  ^gravity  two-pipe  system.  On  the  return  side  of 
the  system,  the  piping  is  arranged  in  exactly  the  same  manner  as  the 
up-feed  gravity  two-pipe  system. 

ONE-PIPE  VAPOR  SYSTEM 

A  vapor  system  is  one  which  operates  under  pressures  at  or  near 
atmospheric  and  which  returns  the  condensation  to  the  boiler  by  gravity. 
The  piping  arrangement  of  a  one-pipe  vapor  system  is  similar  to  that  of 

280 


CHAPTER  15.   STEAM  HEATING  SYSTEMS 


the  gravity  one-pipe  steam  system;  in  fact,  one-pipe  gravity  installations 
may  readily  be  changed  to  one-pipe  vapor  systems  by  making  a  few 
simple  alterations.  The  steam  radiator  valve  is  a  plug  cock  which  when 
opened  gives  a  free  and  unobstructed  passageway  for  water.  The  auto- 
matic air  valve  is  of  special  design  to  permit  the  ready  release  of  air  from 
the  radiator  and  to  prevent  the  return  of  the  air  after  it  is  expelled.  The 
air  valves  on  the  main  are  a  quick  relief  type,  and  the  whole  system  is 
designed  to  operate  on  a  few  ounces  of  pressure. 

TWO-PIPE  VAPOR  SYSTEM 

Two-pipe  vapor  systems  may  be  classified  as  (1)  dosed  systems  con- 
sisting of  those  which  have  a  device  to  prevent  the  return  of  air  after  it  is 
once  expelled  from  the  system,  and  which  can  operate  at  sub-atmospheric 
pressures  for  a  period  of  four  to  eight  hours  depending  upon  the  tightness 
of  the  system  and  rate  of  firing,  and  (2)  open  systems  consisting  of  those 


FIG.  9.    METHOD  OF  CONNECTING  TWO-PIPE 
GRAVITY  RETURNS  TO  DRY  RETURN  MAIN 

which  have  the  return  line  constantly  open  to  the  atmosphere  without  a 
check  or- other  device  to  prevent  the  return  of  air,  and  which  operate  at  a 
few  ounces  above  atmospheric  pressure.  The  open  systems  have  the 
disadvantage  of  not  holding  heat  when  the  rate  of  steam  generation  is 
diminishing. 

Under  the  first  classification  the  essentials  are  packless  graduated 
valves  on  the^  radiators,  thermostatic  return  traps  on  the  returns,  and 
traps  on  all  drips  unless  they  are  water  sealed.  Such  a  system,  illustrated 
in  Fig.  10,  should  be  equipped  with  an  automatic  return  trap  to  prevent 
the  water  from  backing  out  of  the  boiler.  In  this  up-feed  arrangement 
the  supply  piping  is  carried  to  a  high  point  directly  at  the  boiler  and  is 
graded  down  toward  the  end  or  ends  of  the  supply  main,  each  supply 
main  being  dripped  at  the  end  into  the  wet  return  or  carried  back  to  a 
point  near  the  boiler  where  it  drops  down  below  the  boiler  water  line  and 
becomes  a  wet  return.  From  this  main,  runouts  are  branched  off  to  feed 
risers  or  radiators  above,  these  being  graded  back  toward  the  steam  main 
if  they  are  not  dripped  at  the  bottom  of  the  riser,  or  toward  the  riser  if 
the  riser  heel  is  dripped.  Both  conditions  are  illustrated  in  Figs.  2  and  3. 

Return  risers  are  connected  to  each  radiator  on  its  return  end  through 

281 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


thermostatic  traps.  Their  bottoms  are  connected  to  the  return  main 
through  runouts  which  slope  toward  the  main.  The  return  main  itself  is 
sloped  back  toward  the  boiler  if  it  is  carried  overhead;  if  run  wet,  the 
slope  may  be  neglected,  although  it  is  desirably  to  slope  the  pipe  so  that 
the  system  may  be  drained.  An  air  vent  is  installed  at  the  point  at 
which  the  return  main  drops  below  the  water  line.  In  the  simplest  cases 
this  vent  consists  of  a  %-in.  pipe  with  a  check  valve  opening  outward,  but 
certain  systems  employ  special  patented  forms  of  vent  valves^  designed 
to  allow  the  air  readily  to  pass  out  of  the  system  and  to  prevent  its  ^  return. 
A  check  valve  is  inserted  in  the  return  main  at  a  point  near  the  boiler  and 
a  vertical  pipe  is  run  up  into  the  bottom  of  the  return  trap,  which  usually 
is  located  with  the  bottom  about  18  in.  above  the  boiler  water  line.  Some 
traps  are  constructed  so  that  they  will  operate  when  they  are  installed 


TrapN 


Trap. 


Supply  main 


rap 


Hartford 

return 

connection 


ir  eliminating  and 

pressure  equalizing  . 

device-See  note  below*  | 

Boiler  water  line--'3'  ' 


Wet  return^ 


FIG.  10.    TYPICAL  UP-FEED  VAPOR  SYSTEM  WITH  AUTOMATIC  RETURN  TRAP* 

"Proper  piping  connections  are  essential  with  special  appliances  for  pressure  equalizing  and  air  elimination. 

with  their  bottom  as  close  as  8  in.  above  the  boiler  water  line.  On  the 
other  side  of  this  connection  a  second  check  valve  is  installed  in  the  main 
return  just  before  it  enters  the  boiler  (Fig.  11). 

Down-Feed  Two-Pipe  Vapor  System 

In  the  down-feed  two-pipe  vapor  system  the  steam  is  carried  to  the  top 
of  the  building,  the  top  of  the  vertical  riser  constituting  the  high  point  of 
the  system,  and  the  horizontal  supply  main  is  sloped  down  from  this 
location  to  the  far  ends  of  each  branch.  The  branches  are  taken  off  the 
main  from  the  bottom  or  at  a  45-deg  angle  downward,  with  the  runouts 
sloped  toward  the  drops  (Fig.  6).  Thus  each  branch  from  the  main  forms 
a  drip  and  no  accumulation  of  water  is  carried  down  any  one  drop. 
Another  method  of  running  the  steam  main,  which  is  not  considered  as 
satisfactory  but  which  is  practical,  is  to  take  the  branches  off  the  top  of 

282 


CHAPTER  15.   STEAM  HEATING  SYSTEMS 


the  main  (Fig.  7)  and  to  drip  the  end  of  the  main  through  the  last  riser,  as 
illustrated  in  the  down-feed  one-pipe  system  detail  shown  in  Fig.  6.  If 
this  is  done,  the  pipe  drop  at  the  end  or  ends  of  the  mains  should  be 
enlarged  one  pipe  size  to  provide  capacity  for  this  concentration  of  the 
main  drip. 

The  steam  drops  are  carried  down  through  the  building  with  suitable 
reductions  as  the  various  radiator  connections  are  taken  off  until  the 
lowest  radiator  runout  is  reached.  If  the  drop  is  only  two  or  three  stories 
high,  the  portion  feeding  the  bottom  radiator  should  be  increased  one 
pipe  size  to  provide  for  draining  the  riser,  and  if  the  drop  is  over  three 
stories  high  it  is  well  to  increase  the  portion  feeding  the  two  lowest  radi- 
ators one  or  two  pipe  sizes,  especially  if  the  two  lowest  radiators  are  small 

Air  vent  and  check 
Check 

nt= 

From  steam  main 


Boiler  water 
line 


FIG.  11.   TYPICAL  CONNECTIONS  FOR  AUTOMATIC  RETURN  TRAP 

and  the  normal  size  of  drop  required  is  1  in.  or  less.  The  bottom  of  the 
steam  drops  should  terminate  with  a  dirt  pocket  above  which  a  drip  trap 
connection  is  located,  as  shown  in  Fig.  12.  The  returns  on  a  down-feed 
vapor  system  are  the  same  as  on  an  up-feed  system  except  that  every 
steam  drop  must  have  a  drip  at  the  bottom  connected  either  into  the 
return  through  a  trap  or  into  a  separate  water-sealed  drip  line  below  the 
boiler  water  line,  as  illustrated  in  Fig.  10,  in  which  case  the  thermostatic 
traps  may  be  omitted.  The  runouts  to  the  radiators  and  the  radiator 
connections  of  the  down-feed  system  are  the  same  as  those  of  the  up-feed 
system  already  described. 

ATMOSPHERIC  SYSTEM 

The  distinguishing  features  of  the  atmospheric  system  are  gravity 

283 


HEATING   VENTILATING   AIR  CONDITIONING   GUIDE  1938 


return  to  the  boiler  or  to  waste,  graduated  or  ordinary  radiator  valves,  no 
automatic  air  valves  on  the  radiators,  thermostatic  traps  on  the  radiator 
returns,  and  the  venting  of  all  air  from  the  system  by  means  of  pipes  open 
to  the  atmosphere.  The  returns  are  open  to  the  atmosphere  at  all  times, 
usually  by  extending  the  return  risers  to  the  top  of  the  building  where 
they  are  either  connected  together  in  groups  and  carried  through  the  roof 
or  extended  through  the  roof  individually.  Atmospheric  systems,  either 
up-feed  or  down-feed,  are  often  used  where  the  condensation  is  not 
returned  to  the  boiler,  as  in  heating  systems  supplied  by  high  pressure 
steam  through  pressure-reducing  valves  at  locations  far  from  the  boilers. 
The  returns  may  be  delivered  back  to  the  boiler,  if  desired,  by  condensa- 
tion return  pumps  which  are  vented  to  the  atmosphere.  The  return  lines 
in  such  systems  are  simply  gravity  waste  lines  in  which  the  condensation 
flows  entirely  by  gravity  and  is  not  aided  by  any  pressure  difference 


Bottom  of 
steam  drop 


Drip  trap 


Dirt  pocke 


Graduated  valve 


xFloor    / 


V//////////S 


-Connected  to  dry  return 
(where  connected  to  wet 
return,  drip  trap  may 
be  omitted) 

FIG.  12.    DETAIL  OF  DRIP  CONNECTIONS  AT  BOTTOM  OF  DOWN-FEED  STEAM  DROP 


Atmospheric  systems  contemplate  maintaining  a  practically  constant 
pressure  in  the  steam  pipe  and  atmospheric  pressure  in  the  return  pipe. 
When  graduated  steam  valves  are  provided,  they  enable  the  occupant  of 
a  room  to  vary  the  flow  area  to  the  radiator  so  as  to  obtain  a  greater  or 
lesser  heating  effect. 

The  steam  side  may  be  run  as  that  for  either  up-feed  or  down-feed 
two-pipe  vapor  systems,  as  the  conditions  require,  and  the  radiator  con- 
nections are  the  same  as  for  vapor  systems  in  that  they  have  graduated 
valves  on  the  radiator  supply  ends  and  thermostatic  traps  on  the  radiator 
return  ends.  All  drips  from  the  supply  main  and  the  steam  side  of  the 
system  must  pass  through  thermostatic  drip  traps  before  entering  the 
return  system  where  only  atmospheric  pressure  exists.  Fig.  13  illustrates 
a  typical  scheme  of  piping  used  on  atmospheric  systems.  Such  systems 
do  not  maintain  heat  in  the  radiators  under  declining  fires.  As  the 
steam  supply  diminishes,  air  from  the  atmosphere  re-enters  through  the 
open  vent  pipe  retarding  the  inflow  of  steam  and  cooling  the  radiator. 

284 


CHAPTER  15.   STEAM  HEATING  SYSTEMS 


VACUUM  SYSTEM 

In  ^the  vacuum  system,  a  vacuum  is  maintained  in  the  return  line 
practically  at  all  times  but  no  vacuum  is  carried  on  the  steam  side,  and  the 
usual  accessories  include  graduated  valves  on  the  radiator  supply  and 
thermostatic  traps  on  the  radiator  return.  The  air  is  expelled  from  the 
system  by  a  vacuum  pump  and  all  drips  must  pass  through  thermostatic 
traps  before  connecting  to  the  return  side  of  the  system. 

These  systems  are  often  fed  from  high  pressure  steam  mains  through 
pressure-reducing  valves  but  they  may  be  fed  direct  from  a  low-pressure 
steam  heating  boiler  as  shown  in  Fig.  14,  in  which  a  typical  up-feed 
vacuum  system  is  illustrated.  The  supply  main  slopes  down  in  the 
direction  of  flow;  the  runouts  pitch  down  toward  the  riser  if  the  riser  is 
dripped  (Fig.  3)  or  up  toward  the  riser  if  the  riser  is  not  dripped  (Fig.  2) ; 
both  conditions  are  indicated  in  Fig.  14.  The  matter  of  dripping  the 
risers  depends  largely  on  the  height  of  the  riser  and  the  judgment  of  the 
designer.  Ordinarily  risers  less  than  three  stories  high  are  not  dripped 
and  those  more  than  four  stories  high  are  dripped,  but  there  is  no  set  rule 
for  this.  When  risers  are  dripped  the  runouts  from  the  steam  main  may 
be  taken  from  the  bottom  if  desired  and  each  runout  then  serves  as  a  drip 
for  the  main. 

The  risers  are  carried  up  to  the  highest  radiator  connection  and  are 
connected  to  the  radiator  through  runouts  sloping  back  toward  the  riser. 
The  radiators  usually  have  graduated  valves  on  the  supply  end,  although 
this  is  not  absolutely  necessary.  Angle-globe  valves  and  gate  valves  may 
be  used  where  graduated  manual  control  is  not  desirable.  The  return 
valves  must  be  of  the  thermostatic  type  which  will  pass  air  and  water  but 
which  will  close  against  the  passage  of  steam. 

_  The  return  risers  are  connected  in  the  basement  into  a  common  return 
line,  which  slopes  downward  toward  the  vacuum  pump.  The  vacuum 
pump  discharges  the  air  from  the  system  and  pumps  the  water  back  to  the 
boiler,  or  other  receiver,  which  may  be  a  feed-water  tank  or  a  hot  well. 
It  is  essential  on  these  systems  that  no  connection  from  the  supply  side 
to  the  return  side  be  made  at  any  point  except  through  a  trap. 

While  the  best  practice  demands  a  return  flowing  to  the  vacuum  pump 
in  an  uninterrupted  downward  slope,  in  some  cases  limitations  make  it 
necessary  to  drop  the  return  below  the  level  of  the  vacuum  pump  inlet 
before  the  pump  can  be  reached.  In  such  event  one  of  the  advantages  of 
the  vacuum  system  is  that  the  return  can  be  raised  by  the  suction  of  the 
vacuum  pump  to  a  considerable  height,  depending  on  the  amount  of